by not giving a **** what anyone else thinks
just try to surround yourself with your friends or positive people. Facial features change over time(if that's what you are worried about)
Steer clear of him. Do something awesome that shows your talents.
Say something positive and irritating to him or her.
It really does not matter what someone says or does to you unless he/she is right about you.
The only opinion that should matter is his, not anyone else'.