This goes for everything that challenges the mind, ie also studies or exams.
1. Sleep atleast 10 hours.
2. Eat 2-3 hours before.
3. Always think like this: I will do my best because there is nothing I can do right now that can improve my result. That is why I do not need to worry that I won't do my best. I will and therefor I will be calm.
As players I want some insight into the way we approach the challenge of this game Chess.