1. There are things called "power stances". You look like an absolute chucklehead but it pumps you up.
2. Honestly, do some exercise, pushups, weights, etc and then feel your guns. The endorphins are incredible and you'll feel powerful.
3. Recall things you wrote which you're proud of. Forum posts, academic papers, articles, anything. Re-read them and bathe in your own awesomeness.
4. Chew gum at the event. Your brain associates the eating action with being in a safe place. Calms you down.
5. On the day, keep open body stance and be confident. Have a joke or 2 up your sleeve. Say 'Hey, how are you doing?" to a bunch of random people. People mistake confidence with competence and it intimidates them.
All of these are proven psychological tricks that will make you invincible.
Oh .. and only roll hits and crits!