This may seem counterintuitive, but over-practicing may get you to a spot where you become overconfident in your abilities. You may take things for granted and not focus on what needs to be done during the actual performance. If you go into a performance knowing that your mind needs to be in the game in order to do your best, you will not have as much room for anxious thinking. Being present enough to focus on your skill and technique can stop you from overthinking beyond your capabilities.
Before a big performance talk through the experience with someone who has been there. Imagine what you might hear before you get on stage. Think about what things you will see as you walk on stage toward your piano. If possible, go to the performance venue and do a physical walkthrough of your performance. Thinking about the sights, sounds and smells before you go on stage can give your mind something sensory to focus on rather than worrying or catastrophizing about certain aspects of your performance.
Just before each performance, it is important to take the time to get your mind in the right place. Find a focal point for your eyes. This can be somewhere on your sheet music or somewhere past the piano. Tell yourself the first thing you will do when you begin to play. Take a deep breath to calm yourself physically and get rid of muscle tension. Shift in your seat until you have found your best posture. Finally, when it is time to begin, do not hesitate, just trust yourself and go for it.
If you are eager to become a performing pianist, join the Bachelor of Arts in Music with an Emphasis in Piano Performance degree program at Grand Canyon University. You will learn technical and performance skills that will make your career flourish.