Desire, expectation and attachment are the three pillars of evolution and growth.
Contrary to the advice of most gurus and enlightened beings, they should be embraced, but properly so. At least this is what seems pretty clear to me, but then, I am not enlightened :/ Allow me to make my case...
Understanding desire is both quite simple and quite complex. On a visceral level hand, desire is easily understood as simply "wanting," but there are many forms of desire. Our reptilian fight-or-flight response is a result of our desire to not die when faced with danger. Slightly up the survival spectrum comes our desire for food, clothing, and shelter. Our desire to reproduce is just as strong, and may even exceed our desire to survive. All of these desires can be directly mapped to biological programming that can be traced back to our most ancient predecessors, all the way down to microbes, eukaryotes, and viruses, the first forms of life.
When we think of desire, however, we tend to think more along the lines of love, passion, wealth, health, or the general wanting of something far beyond the basics of survival, at least in our own minds, but it is clear that the desires of the microbe and of modern man are essentially the same: survival, resources, and procreation. There is one exception, the desire to self-express, which is a relatively "new" form of "procreation", which I'll bring up shortly.
The actual definition of "desire" specifically references this:
-- Oxford English Dictionary
Everything that lives, grows. Everything that grows (and only things that grow) are DNA-based. Nothing that is DNA based does not grow. Therefore, it's safe to say that anything 'alive' must grow and anything that grows must be 'alive'.  This need to grow is made especially clear when you consider that all life on earth evolved from one single cell that came into existence 3.5 billion years ago. at least according to one study 
Only two things are needed to guarantee growth.
These two prerequisites encompass pretty much all of the expressions of life and their complex, and often bizarre, interactions. Not surprisingly, they are also hardwired into the very thing that makes us 'living", our DNA.
Therefore, it seems reasonable to presume that all desire is based on our need, our genetic demand, to grow, and that need is as fundamental to our existence as DNA is fundamental to life. It would be easy to argue that desire itself is a form of need, and what we need is, for the most part, genetically predetermined. It may not seem that way at times because we are always in the process of growing, and that growth has needs, but it is only over many, millennia that we learn what needs are effective and what needs are useless. This knowledge is them recorded in our DNA. This is most evident in the fact that humans are born with an innate fear of loud noises and of falling, but aside from these most obvious traits, there are countless more stored in our DNA as a result of our past experiences. We do not know now what we will need in the future to survive as a species. The only way to address this challenge is to ensure that all forms of growth are explored and allow the circumstances of the moment to determine which ones are best suited. Even with this modal of evolution, there is still only as 0.1% survival rate over time as 99.9% of all species that ever existed have gone extinct.
Typically, this growth is physical in form, in that the creative abilities of pretty much all life forms that have not yet developed a prefrontal cortex (or equivalent neural processing abilities) are limited to reproduction as their creative expression. For those lucky enough to have a prefrontal cortex, we may opt to "grow" in ways beyond simply reproducing. This we call "creativity," and it can take many forms that find their roots in "ideas."
Since we began to develop a prefrontal cortex about 70,000 years ago we have found ever more creative expression in art, beliefs, inventions, and philosophies of every shape and size. This was the birth of self-awareness and self-expression, a creative form that didn't exist for the first 3.5 billion years or evolution. The more spiritually dedicated believe that the highest form of creativity is to redirect our creative energies typically used for reproduction into non-physical forms of creation. Exactly what is being created is understood differently depending on what philosophy is being practiced, but in all cases that form of creative expression is said to be of a supernatural nature, i.e. kundalini, chi, prana, etc.
For some, the DaVincis, Van Goghs, the anonymous prehistoric cave painters, this creative drive is as strong for them as the desire to reproduce is for salmon, and perhaps just as fraught with danger. A salmon will die attempting to swim upstream to return to his place of birth to lay their eggs, if a bear doesn't eat her first. Some creative types also will lose their life, or their mind, in an attempt to satisfy their creative desire. That is how strong the desire to create is.
From a metaphysical/esoteric perspective, life is the expression of energy, in that where there is no energy, there is no life. But what of the atoms themselves? They have a tremendous amount of energy when there is no life, for example, the atoms is a rock? Well, what is an atom? It is a positively changed probability wave, a negatively charged probability wave, and a neutrally charged probability wave that together have the greatest probability (i.e. requiring the least amount of effort) of collapsing into one of a finite set of predetermined organized structures that is an atom. What would an atom be without any energy? It would be nothing more than a concept, a law, a mathematical construct. (I address this in more detail in my post Teonanacatl Speaks - Lesson1). Once energy is applied to this (and other) laws, reality comes into existence. The metaphysical question is less "where" did this energy come from because metaphysical models imply a reality beyond (meta) the physical, so the "where" axiomatic, but more about the mystery of "why." The esoteric answer to this is simply "desire." That which created this reality did so because it was the desire of the creator to do so. We don't have to understand what the desire was, just simply that the desire to create exist(ed/s). This is not a new idea and can be found in ancient Eastern, Greek, and even hard-core Roman Catholic beliefs.
The implication here is rather stunning (to me), which is, all energy is an expression of the desire of whatever created this reality. But more so, the self-organizing nature of this energy (implying that the energy itself is a form of life, as self-organization is an attribute of life) ensures that the creative expressions of this energy would grow in a manner that was, to some degree, predetermined. DNA would, therefore, represent the most refined expression of this creative energy of life, that we know of.
Expectations can only be a product of a consciousness that has the ability to think abstractly, to plan, and to consciously remember. This is not limited to humans by any means. Crows have clever strategies to chase squirrels into the road as a car approaches knowing that there is a chance the squirrel will get run over by the car, providing an instantly prepared and tenderized meal. Birds of pray will pick up burning twigs from the edge of a forest fire and carry that fire to new places to start new fires knowing that it will flush out hundreds of edibles into the open.
Clearly, if they did not have expectations of getting a meal they would not be attacking squirrels and spreading fires. Pretty much everything we humans do we do with some sort of expectation. In fact, expectation is probably the biggest driving factor in evolution, because actions are only taken when it is expected that they will result in certain outcomes. In the past, those that have calculated wrongly, cease to exist. Today, being completely out of sync with reality has only minor consequences.
The question of expectation is not whether one should have them or not because clearly, expectations are a necessary part of decision making, but rather how one understands or deals with the results that vary from the expectations.
It was once believed that sacrificing virgins and/or tearing the beating hearts out of the tribe's most accomplished warriors would please the gods, who, in turn, would bestow good crops and protection from bothersome neighboring tribes. The reason we don't do this today is that the results of this practice did not match expectations (a lot of dead virgins and warriors accompanied by drought and increasingly obnoxious neighbors), and eventually more predictable methods were found to control crops and neighbors, which came to be what we today call science and politics.
When expectations are measured against reality we learn, evolve, and develop a better understanding of the reality we live in. When we are upset, depressed, disappointed, angry, etc, that our expectations failed to be realized, we are simply demonstrating our inability to learn from our bad judgment. This is what we call "attachment."
Ignorance is well correlated to attachment, because if one is too ignorant to recognize the difference between reality and expected results from their actions, then they will remain attached, or committed, to their useless practices. This is most evident in parts of the world where the more ignorant continue to believe in such insanely stupid ideas from flat earth and rumpology to "Virgin cleansing," where it is believed that raping a baby or a virgin will cure aids. Sadly, we are also seeing examples of this in epidemic proportions with first-world young people getting degrees in useless studies (as far as the job market is concerned) expecting to survive in the real world. 
The same holds true for attachments to personal expectations. It's expected, even necessary, to have expectations based on our actions and our environment, which for most people includes relationships, work, health, finances. These expectations are a testing ground of our beliefs and assumptions about our world.
Desire is what drives all creation. Expectations are the application of our knowledge in the real world.
It is not desire or expectation that is the cause of suffering, it is our attachment to our beliefs as to what the expectations of our actions, motivated by desire, should be, rather than seeing them as what they are and adjusting our worldview to be compatible with the reality you live in.
The suffering from attachment (i.e. when you suffer because you didn't get the desired outcome you expected) is really a culturally accepted form of narcissism because it is an irrational self-centered worldview to expect that circumstances in the objective world should in some way be dependant on your personal desires and/or the inability to understand the reality you live in. In my option, what validity there might be in the "create your own reality" philosophies is lost until one realizes that circumstances do not matter, but how we respond to those circumstances does.
Unfortunately, much of our modern society and the pillars of its current state, such as education, media, and politics, is not based on attainable desires and reasonable expectations but on appealing to the childish, ignorant and narcissistic attachments of the ever-growing numbers of those that evolution would have quickly evicted from the gene pool not that long ago. This is especially evident in morality-based beliefs (as opposed to fact-based), such as religions that promise a heavenly afterlife of eternal happiness, or politicals (the religion of the state) that promised free education, free healthcare, free housing, and free food (socialism/communism/Marxism, etc.). These are examples of beliefs that are fueled by our most primitive desires and are shored up with profoundly unreasonable expectations that are promoted by those who benefit from the suffering of others. Any slightly aware, moderately intelligent person would abandon any and all attachment to such desires and expectations after realizing not only the folly of such a position but the destructive, painful consequences that such attachment would create. Unfortunately, slightly aware, moderately intelligent people are shrinking in numbers as a result of the attachment-promoting culture we are being raised in.
Detachment is the only way to find peace and regain your inner power, which is really the only power you have, while at the same time, removing power from any and all external forces, from nature to politics. This certainly does not mean that liberating one's self from attachment guarantees better condition in life, but it will ensure one does not become a slave to unfulfilled desire and ruined expectations.
 I said "DNA based" because not all viruses have DNA. Many operate off of an RNA genome. HIV, the virus that causes aids, is an example of a virus whose genetic material is RNA, not DNA, however, it is DNA-based, as RNA could not exist without DNA, and visa-versa. The RNA based viruses are capable of replicating and evolving, therefore, they are alive in the strictest sense.
 My logic is pretty simple, and I think it conforms to the basic transitive law of logic and set theory. Everything that is in Set A is in Set B Everything that is in Set B is in Set A Everything that is not in Set A is not in Set B Everything that is not in Set B is not in Set A therefore everything that is in Set A must be Set B, and everything that is Set B must be Set A.
 https://en.wikipedia.org/wiki/Rumpology, apparently my rump is that of a very negative and sad person. Now I am sad, but hey, fuck them!!
 The Most Useless College Majors, https://www.ranker.com/list/most-useless-college-majors/school-buddy
 All Species Evolved From Single Cell, Study Finds, https://news.nationalgeographic.com/news/2010/05/100513-science-evolution-darwin-single-ancestor/