As an actor, you don't often get a chance to know exactly the impact of what the audience is seeing, even though you can ask where the frame is. A move that feels tiny can be huge, and vice versa.
First, do enough training. Then believe in yourself and say: I can do it. Tomorrow is my day. And then say: the person in front of me, he is just a human being as well; he has two legs, I have two legs, that is all. That is mentally how you prepare.

