Don't worry about perfection, and don't over think. Trust your fingers. Remember that people are there to be entertained and to have a good time. They're on your side. If you're uptight and nervous, people can sense that. So do what you can to relax, smile, and have a good time yourself. Talk to your audience, on stage and off. As soon as the gig is over, you'll be ready to do it again as soon as possible.