I'm a classical guitarist and I have horrendous stage fright. I think there is a meeting for us two doors down from AA.
Yes, of course you must be prepared - FULLY prepared. Your performance pieces must be mastered or you're bound to drag that lack of skill onto the stage with you.
But just as we master our repertoire, so must we master performing.
We need to perform OFTEN. The more we do, the more comfortable we become with it.
If ever I have a large performance looming in the future, I immediately set up as many small performances as I can in order to get the willies out.
Doing this does not stifle me musically as it might a proficient performer because I can hardly comprehend what I am doing until the third or fourth time anyway.
By the time I get around to the actual performance I'm calmer and I can actually start to enjoy the music I'm playing... until I make a mistake. LOL!