The Path To Despair Is Paved With Shattered

To desire is to want something that one does not have but wishes to have. In most cases, when a person desires someone or something, they firmly believe that there is some means of slating that desire. Whether or not those means are available to the person with the desire can vary drastically from person to person. While desire has been seen as a great motivator (Alexander the Great's conquests are often said to have been fueled by his desire for more world to conquer), it may also prove to be the undoing of a person's mental health, with the most common side effect being prolonged cases of depression. Sadly, for some people, having something they desire be utterly out of their reach can often make them willingly allow themselves to go into states of melancholy and despair.
Humans, by nature, want things that they cannot have. This has never been disputed throughout history and, in most cultures, is accepted as a part of human nature. People have a tendency to want things, even when logic would dictate that those things are out of their reach. In some cases, this has been a positive thing that has allowed people to achieve their dreams, but disaster can strike when a person fails. For some people, desiring something they cannot have can often make them feel inadequate or unworthy of whatever it is they already possess. For others, it can cause fits of violence and rage, typically accompanied with attempts to used flawed logic to blame someone or something else for their inability to get what they want. However, perhaps the most damaging effect that the inability to fulfill one's desires might have is the onset of depression.
When someone develops a case of clinical depression due to being unable to fulfill a personal desire, the consequences can weight heavily. In their minds, the only way to lift their negative emotions would be to find a way to fulfill their desires, preferably in a manner that satisfies them. For example, a man who is in love with a woman and becomes depressed at her lack of feelings for him might become depressed. While having her openly admit to having feelings for him would alleviate the problem, it would only have a lasting effect if it was brought about in a manner where the woman did not appear coerced or manipulated into such an admission. While it is possible that some people would have no scruples over accepting a lover under false pretenses, the depression might become replaced with paranoia in the long-term. After all, if she was only manipulated into loving him, wouldn't it be just as simple for someone to manipulate her into eventually leaving him?
It is true that not all people who have failed to fulfill their desires become depressed individuals with compromised mental health. However, it is generally viewed as a safe assumption that letting someone brood for too long over being unable to accomplish a goal can lead to a state of melancholy and depression. There is a silent consensus that a majority of the population would have to face several failures to drive them to utter doom and despair, but for some people, just a single catastrophic failure is enough.