Whether you're performing for grandma or the entire school, an examiner or the entire church congregation, stage fright happens. Your heart beats a little faster, your breath becomes more shallow. Maybe your hands get a little trembly.
It happens to everyone - even the pros! Check out some of these quotes:
“The terror of performing never goes away. Instead, you get very, very comfortable being terrified.”
~ Eric Whitacre, composer, conductor, 5th member of Depeche Mode ~
"I have had a very difficult time with stage fright; it undermines your well-being and peace of mind, and it can also threaten your livelihood."
~ Renee Fleming, soprano ~
"Because you get very nervous, sweetheart, you have to get this spot right 11 times out of 10 at home so that you can get it right 10 times out of 10 on stage."
~ Irina Ginzburg, piano teacher, pianist (to me) ~
So what's a musician to do? Well, as my one teacher, Irina Ginzburg was getting at, you need to know your music well. So well that your nerves can't get in the way. That means, you need to practice mindfully.
Another thing I've learned is that, it's not all about you. When people are listening, they are listening to the music. To the soundscape you are creating. Unless you're making weird faces and gestures, or wearing something distracting, they're really not focusing on you as much as you think they are. So don't worry about whether they thought "Oh dear, she messed up in Bar 23." Most likely, they don't even know. Depending on the performance setting, they really don't care about that "blip". If they don't care about it, then you shouldn't stress out over it.
Here's another point that I cannot stress enough: practice performing. At university, I was performing nearly every week. Our practice rooms had windows in them, so anyone could peek in and listen to you. I learned to manage my nerves then.
Now, I play in a church choir. I alternate with another pianist/conductor so we're "on" nearly every week in one way or another. Once, I had my hands in the wrong starting position for a part of the Mass. No big deal, I just calmly moved my hands to the correct position and the choir carried on. When hymns are changed at the last minute, I wind up chording and sightreading. Another time, I messed up cuing in the choir so we all fumbled a bit until we found our way. It was one of those funny stage moments, so I bent over laughing, while one hand continued to conduct.
Sometimes, I botch chords. Sometimes, my improv doesn't sound so pretty. So what? The choir and the congregation are still singing. I just have to join in on the next bar. Next time will be different.
Now, if I only played at church once every two months or so, then I'd feel a bit more pressure. However, because I play or conduct on a regular basis, blips here and there aren't a big deal. The more you perform, the more you learn how to handle your nerves.
The music goes on, there simply isn't any time to obsess about it. Just do the best that you can in that moment - be present in that moment - and move on.
Here are some articles with tips on how to deal with stage fright: