When you go onto the bench from leaving the game, you can't help but smile at the high fives you get. There are many ways of making someone smile on and of the court, field, etc. Even the general high five boosts up peoples spirits, which also means they feel better about themselves, so their self-esteem goes up. There are the times though that everyone looks away from you, especially when you get older and it gets more intense. Those are the times that many teenagers will let themselves get down. The link above highlights the positives to sports and self-esteem, while this video shows the truth about what teen athletes think of themselves, and how it may be dangerous.
In conclusion from theese two sources you may have your own opinion, but in my mind I would like to say that sports tend to get worse for you as you get older. When you get older you are closer to trying to become one of the famous athletes. When you are younger though, it doesn't tend to matter to you as much because you are just out there to have fun. So as long as you don't let anything get to you and bring you down as you get older, sports are healthy for you, but if you pay attention to EVERY single little detail, it is dangerous for your self-esteem.