I think i can answer this question bcoz sometime for me its hard to stay positive even if i had a good contest with positive change in rating.

First of all just stop comparing yourself with your friend. Its hard but you have to do it.

Second, after the contest i feel like hit by hard rock and i fall down but i have to get up to fight again, this is the only way to become strong. Just find out the mistake you have done in contest, what you need to learn to level up and just decide the next step then start working again.

How about staying neutral? Consider contests as a game. You play games when you feel bad. If the game doesn't help, then something is wrong with the game.