Everyone has desires, there's no denying this fact. To say that you do not desire a thing in your life is like saying you are not alive. Desires can be large or small, private or public. They can be anything. So instead of trying to define what a desire is, I ask these questions: Why do we desire? What good or bad can come from them?
Even the happiest person in the world still wants something more. A person who is most content with their life, satisfied with its direction, can still desire for something. Face it, it is human nature to always be wanting something that you don't have. Even if you possess everything that you had once desired, you'll want those things to be better or you will want for more. Why is this? Maybe because no matter where you are in your life, something or someone is going to tell you that your life could be better. Technically, you don't even have to be told that things could be better. Subconsciously, every single person out there strives for a better life, the best life they can have. There is no real explanation for human desire because it is in our nature and as most of us know, human nature can not be perfectly or fully explained or defined by any means. So, desires often have an unknown cause but they can also have a known effect.
There is a difference between a "good" desire and a "bad" desire. I'm not talking about the desire to make someone happy or the desire to harm someone, those are pretty obvious. I'm talking about the effects of desires, not the consequences. Those who become obsessed with their desires allow them to take over their life. Even if these desires are for the common good, what a person does to satisfy their obsessions can be negative. Think of desires as drugs. What does an addict do to get their next fix? Many things like steal, lie, cheat, harm others and worse of all, harm them selves. Those who are consumed by their desires can do good as well. They can work hard to achieve their goals and not cut anyone down in the process. Even if these goals are never reached, they can be satisfied with the fact that they've tried their best and have become better because of it. Not everyone is the same, therefore, not everyone will have the same attitude towards something.
We are born with many instinctive desires, including the most vital one, which is the basic desire to live. Since desires are necessary to the maintenance of human life, they are in that sense beneficial. But simply to pursue desires with no higher aim is to become a slave to desire, and this can lead only to misfortune for oneself and others.