I recently gave some Performance advise that I follow to great effect.
A few thoughts.
1 When you feel you are ready practise performing your pieces under pressure i.e. tell people you are giving them a performance and would like them to critique what they have heard. Look your audience IN THE EYE, face up to them before you play a single note. Take your time, then only when you are good and ready, begin.
2 Record your own performance and imagine you were giving feedback to someone else.
3 If you have areas that need work, practise those areas at slow speed and with CONCENTRATION, the slower the better and NO DISTRACTIONS. Build up speed one metronome increment at a time maintaining masterful controll. Use any technically difficult passages for daily drills.
4 Perform in a variety of locations. Ever went to do something then forgot what you went for? Then only when you go back to where you originally had the thought do you remember again. Thoughts can become geographically triggered, including your thoughts about the music you study. So to bypass this, perform in lots of different locations. If you know the whereabouts of a piano that is not your regular piano, ask permission to give a performance on it.
5 Oh yes, GIVE YOURSELF PLENTY TIME! The body (the subconscious) needs lots of time to KNOW a piece of music on many dimensions. Julian Bream (classical guitarist) said he'd have a piece in practise up to 2 years before he'd consider that he knew it, and even then it was still developing.
6 Last, remember why you play in the first place, your joy of musical expression. If a piece turns into a disaster, don’t resent the piece, forgive it, forgive the situation, forgive yourself; bring your self back to a feeling of piece with the music or stop playing till you feel open to it again. I have heard many students (and teachers) cussing under their breath when things haven’t gone well. Imagine an artist trying to paint on top of a canvas that is violently being disturbed. How can you ever hope to master the music when you haven’t even got control of yourself?
Best to all.
Peter.