We all make mistakes. It’s a fact of life. And some of those mistakes are bound to be made in front of other people, during a test that is highly important, or both.
The instinctual thing to do is to look over and see if anyone noticed. Chances are they’re going to notice you looking over more than they noticed the mistake. Don’t express your mistake with your face – it just makes it more obvious.
The other, more long-term effect mistakes like these have is the loss of confidence. But the loss of confidence will just make more mistakes. Keep going – maybe that was the one mistake you were bound to make anyways.
The best thing to do after making a mistake in front of an audience is to pretend it never happened. If it messed something up, secretly try to fix it.
For instance, if you’re performing on the violin to a recorded piano track, and you mess up, pretend it didn’t happen. Then slyly change the next couple of notes so that you’re back on time with the recording.