Shakespeare referred to jealousy as the "green-eyed monster" in Othello. Envy is its cousin–the unnamed beast.
The two emotions are related but different. Jealousy involves at least three individuals where there is competition for affection or attention. Envy only requires two–you and someone else
As envy is likely more common, it can be more damaging. Religious traditions have spoken of it as one of the "deadly sins. And it is so ingrained into our consciousness that it must be recognized in order to deal with it.
It is clearly connected to the competitive nature of existence. We all feel insecure about our position in life, be it professional, financial or personal. There are "issues" we have with all of the above. When we encounter someone who seems to have resolved an issue that bothers us we reflexively feel envious–why not us? Why didn't we get that job? Why isn't our spouse as attractive or successful? What about our children? Why couldn't they be like their kids? Why I am I suffering from physical or emotional issues and they seem so healthy and content?
The quest for serenity/happiness is completely tied in with envy. Our lack of either makes us vulnerable to envy.
The problem is that envy is a completely negative emotion. By its very nature when we feel envy we feel other negative emotions–sadness, anger, frustration. These emotions have physical consequences (as do all feelings). We may feel a facial flush, our pulse and blood pressure rise, our intestines churn. The very happiness we seek is pushed further away which only makes us more envious. It is truly a monster in its own right.
The irony is that envy makes very little sense. We usually pick and choose one element of the life of someone else which we would choose for ourselves. We fail to realize that every life is a package deal. You might envy one aspect of Joe's life but not another. Even if you could trade for that one aspect, you would get it all! How foolish to even "go there".
Besides, from a spiritual perspective each life experience is unique. Each element of adversity is an opportunity to evolve and grow by how we deal with it., Each life has its share of joy and sorrow, success and failure. Some seem disproportionate to other lives. Who says life has to be "fair"? There may likely be past-life and karmic issues that each life must face which are unique to that individual. So it makes no sense to make comparisons with others.
Facing the success of another and how we deal with it is another challenge. Do we share in the joy of others or prefer to compare our suffering with those who have lost more? Do we actually enjoy the pain of others?
How we deal with the "monster-without-a name" says much about our spiritual state of being.
We can all learn to handle the beast better.