It took me a while to learn to perform well when competing. Performance for me mostly came in the shape of a racket sports competition at the time. But, it's been the same for other things too (music, work, sports, etc). In college I was able to come up with 3 rules for performing:

1. - play your very best, always
2. - play the next point better than the last
3. - don't be silly, which means not doing anything that could interfere with 1 and 2.

This model has helped me a lot not just in racket sports competitions but also in life.