Well it's human nature to want what you don't have, one of the core principles of economics is that human want is insatiable. It's only natural to envy someone who's successful or better yet, more successful than you are and this is because he/she has more than you do.

When you see someone that's more successful than you are, you can react in 3 ways

1: Be happy for them: These days, this has become the least popular reaction because most people don't want anybody to do better than they are

2. Envy them: From time immemorial, even dating as far back as Cain and Abel, Jacob and Esau, human beings have always envied people who are doing better than them, simply because we want to do better than everyone else. People that envy others often don't want the people they envy to do badly or not be successful, they just want to be more successful than they are.

3. Be passive about it: Some people just don't care and whether or not you're more successful than they are doesn't matter to them. They'll go on living their lives like as if nothing happened.