This is how it works:
You get a certain amount of xp during your game (depending on how you do). We'll say you get 500xp every single game. Exactly 500xp.
With a Psych Profile, you get bonus xp each match. The bonus xp is added to your 500xp at the end of each game.
So you can do really well in one game and get 1000 bonus xp from your Psych Profile. That will be added to your 500 for a total of 1500xp at the end of the game.
Maybe the next game you do poorly. You don't get any bonus xp, but you still get your 500xp.
The penalty for the Psych Profile ONLY affects the BONUS xp that the profile would be giving you anyway.