Just remember that you will screw up. It will happen. Let it. No one ever notices. They don't know it's your first time on stage. Great example: Friend of mine was on stage for the first time. First song: Night Visit (Pretty Fair Maid...many other names) He got to the line about
"I got up and I made the bed, and I made it nice and easy." He, however, sang:
" I got up and I laid her down, and I laid her nice and easy."
His friends rolled, he turned red, and no one else noticed.
He still performs that verse at sessions...the second way.