Oh man, there are a BILLION different tips one could give for both performance and competition! Best thing I could possibly say is this: Do something YOU are proud of!
My best example of this is thus: I have never won anything, quite literally. I’ve always been one of those “consolation/thanks for trying” sort of prize winners. I never believed in being proud of myself, because I was crazily afraid of being prideful. I’m weird, I know. BUT, recently for a class we had a “Pitch your story” competition, in which we could win a very nice portfolio. I looked at that and said “I’m not going to win that, so… instead, I’m going to make something I am proud of!”
I won the thing. I was shocked.
Also, another good example: Felix Cane is seen saying, before her performance that she won the first Australian competition she competed in, “I’m not really here to win, I’m just happy to be in it.”
I agree with JSheridan on all the other points. 🙂