"How all the other passions fleet to air, as doubful thoughts and rash embraced despair and shuddering fear and green-eyed jealousy!"

Envy is an emotion that "occurs when a person lacks another’s superior quality, achievement, or possession and desires it." They also feel that it is not possible (or not easy) for them to have what they want. Otherwise they would simply go get what the other person had, and they would be satisfied; Envy is one of the seven deadly sins.

At the core of envy seems to be a "social comparison" that threatens a person's self-esteem: Another person has something that the envier considers to be important to have.--often rooted in the envier feeling low self-confidence, and they feel that they need to be or have the same things as others. If they don't have it, or they can't have it, they feel envy.

However, what is envied could also be something that is only of personal importance to the envier, even if what the other person has is of little significance.

What is the purpose of Envy? What does having envy accomplish? At one point or another, we have all been guilty of jealousy or envy, but to what extent? Most of us, have had a envious or jealous thought—when someone we see is dating someone we are attracted to (could be a celebrity or a friend), when one of our peers owns something we cannot afford, when those around us have better relationships than we do, or when a family member accomplishes something greater than we did. It comes in every form. But how far do we let these feelings go? When are the boundaries crossed? It seems to me that some of us don’t even notice these feelings and it is a blip in our lives, never to be thought again. Then there are those that think about it from time to time, but don’t let it effect their lives. And then you have those who cannot let it go. Those people who let these feeling eat away at themselves, to fester and grow into something more. A problem, an issue. Resentment, betrayal, and frustration set it. You start to feel abandoned or left behind. You wonder why you can’t have this, why you can’t attain it. Instead of working towards a goal you set, you begin to fall behind the anger and resentment. You don’t move forward, you create aggression and bitterness.
I’m not sure why some handle this better than others or why we even have these feelings. Most things in life are attainable; are within reach. Hard work and strength of mind always seem to pay off. If you want something bad enough, you can get it within reason. Why are some willing to work for what they want and others willing to go through the agony of watching others attain success?