Here are some ideas from our recital handout to get you ready for that single performance. Ping-Pong balls. Once a day get someone to try and distract you while you play and/or sing. They can do anything at all except physically obstruct you from performing. So, they can throw ping-pong balls at you, or get really close and stare at you, or try to make you laugh. Learning to ignore them and play/sing your music great at the same time will help you learn to concentrate and focus during the performance.
Swallow the Egg. Don't just get your piece in half way - internalize it, make it a part of yourself. Master it. Make the song your own.