Emotions are there to help us; orient us within ourselves and around others. Being jealous is a lot like being angry. Anger helps us know when we feel we have lost something so we can tell others and check it out, see if it is true, if another deliberately took something of ours or if it's a misunderstanding and they had no clue we felt that way and/or we then know more about that person (if a boss took credit for something we did, for example, we discuss it with them to see "why" and if we don't like/agree with the reason we know we need to change jobs or get more education and become the boss or do something so others can't mistake who the creative/smart person is, if that's what we want) and when we are jealous, we learn what we want.

The emotion is just information, not something to be focused on in and of itself. "I wish I had won the lottery instead of John, I deserve it more than he does" tells me important information about myself and what I think of John. It's not about John and his winning. I may think I think the lottery is a stupid way to spend one's money so, learning that I'm jealous of John for winning it, might tell me different, more of my "secret" desire for money, gambling, and winning, etc. or that I think I'm better than John. All of that is things going on in my heart that need addressing and it's good to know them so I can think about/work on those issues I might not have recognized I had before.