The symptoms of stage fright come from the release of the hormone adrenaline. A shortness of breath, pounding heart, tingling ski and even a chilled feeling can be some of the sensations. The response is a natural one in people for whom public speaking or performing triggers the "fight or flight" reflex. The comedian Jay Mohr has terrible stage fright and has successfully combated it. However, by understanding that most of this anxiety comes from the anticipation of negative response will help you respond to these dreaded feelings. Keep your mind in the now and mentally rebuke these thoughts that you have conjured on your own.
Stage fright is an anxiety response to a performance in which the performer does not feel rehearsed. Preparation can help. For example if you are reciting a poem, know it backwards and forwards. If you are singing the Star Spangled Banner, practice until you're able to sing it in your sleep. Readiness will reduce performance anxiety ten fold. A juggling axiom for pre-performance jitters is called the seven p's: "proper prior preparation prevents piss poor performance."
Secondly, look at the performance from the audience perspective. Being on a stage gives the performer power over the audience. Use this power as a tool. Whatever reason you are there and whatever you are doing, you have been asked or hired because you are good at this particular activity.
Breathing:
An attack of sage fright can be exacerbated by shallow breathing. Breathe deeply through your nose, filling your diaphragm; exhale through your mouth. Close your eyes and concentrate on your power and preparation. Let the oxygen fill your body, your practice fill your confidence and relaxation fill your mind.
Mantra:
Some performers believe chanting mantras ("I can do it"; "I'm ready") before a show is helpful. This is a personal endeavor and should be used in accordance with how it makes you feel. If it works use it, if it does not, then mantras are simply not the solution for you.
Whether delivering an acceptance speech, reciting Shakespeare or juggling chainsaws, successful performers fill their minds and hearts with confidence. You are there to entertain and/or inform. Be confident and enjoy the moment. Being on a stage of any form can be exhilarating and the moment should not pass without notice. Be prepared, don't forget to breathe, fill yourself with positive confidence and claim your power.