Take it one match at a time, don't try to win the whole thing, just try to focus on winning your current opponent.
Breathe, remember you are ok right now and you have trained and you are ready. Breathe and be well.
Keep with your normal eating routine, nothing unusual. Unless you were cutting weight, focus on rehydrating (water and electrolytes, e.g. Pedialyte, eat your normal food or bars you are familiar with).
You will dictate the pace of the match you are going into. You will play into your game. You will not let them into their game. You will go for it. Get your grips, don't let them get theirs, go for your takedown or your pull. If your technique fails, thats ok. You dictated when the action took place and when it started, which means you will be first to react even if they stuffed your takedown/guard pull. You know when the action happens, you are ahead of the game.