Boost your own energy levels by having a talk with yourself before each performance. Remind yourself that you are a good performer, and that this is what you love doing. Finding a mantra such as "I am great at what I do" is also helpful.
Look at the audience, and remind yourself that they are there to see you. Remind yourself that it doesn't matter what they think, and that what really counts is what you think of your own performance.
Breathe deeply, when possible, while the performance is taking place. Taking slow deep breaths just before you go onstage, or during small breaks, will help slow your heart rate and get rid of the jitters.
Warm up your body. Jump up and down when you can to release some of your nervous energy. Pacing, jumping jacks, drumming your hands and lunges also work. Whatever physical movement you can do that will make you less anxious will do.
Remind yourself that every audience wants to see success because failure makes the performer and the audience uncomfortable. So, let the audience's positive energy flow into you and help you beat stage fright before a performance.