Positive:
It helps your body stay active and healthy. Will not be a problem when it comes to keeping your body in shape. Also, it gets you to socialize with people that you know or don´t know and get better with your social skills.
Negative:
If you play a sport that has a lot of contact involved, you can get injured and hurt an important part of your body. When you get older, it may be hard to move a particular part of the body around.