Les, are you a solo performer or a sessioneer (I can only speak from experience as a solo performer)?

Start with something you know very well, one of your 'best' numbers.
Don't get into the difficult stuff until you're well 'warmed up'.
Do not, under any circumstances, attempt to bolster your confidence with alcohol or any other intoxicant - the only person who thinks you're performing better when you're pissed is you! (The Greatest Lesson I ever learned!).

The adrenalin's the cause of the 'survival' thing - it happens to us all, the important thing is learning to control and channel the 'fight/flight' energy, and some of the excellent earlier posts give ways of doing that, you just need to experiment and find a way that works for you.

Good Luck, feel encouraged and keep playing!
J :0)