NiketaCalame says when dealing with stage anxiety:
I would suggest getting to the theater earlier than the call time if you can. Bring your ipod and listen to a calm song that is one of your favorites or your characters favorities do a relaxation exercise. Lay on your back (if its clear do this right on stage). Tense and release your muscles one at a time from your toes to your legs to your abs to your arms to your face. Do this a couple of times. Then do this again in your chair in the dressing room or green room when house opens.
You also have to remember its not about you its about the story and the character. If all else fails use it. Think to yourself "might the character be nervous or have anxiety" about an event in the play and see how that can inform your behavior as you play on stage.