1) Don't take yourself so seriously. You aren't solving all the world problems, and this gig won't make or break you. You are just playing music and having fun.

2) Audiences are far less critical than you are.

3) You are up there with your band mates. People aren't only focused on you. The rest of your band can fill in the mistakes.

4) It's a live show there are supposed to be mistakes and surprises, that's what gives it character.

5) Print out the lyrics and music and put them where you can see them on stage. You may never have to use it, but knowing they are there may make you less likely to freak out.

I also never add a song into the set list I can't play drunk, but YMMV.