Get a hold of yourself, girl!!
Don't ever let your emotions get the better of you when giving a musical performance, PARTICULARLY a performance on the theremin. I know it feels yummy and scrumptious as you're transported into the flow of the music, but it will interfere with your technique. The problem is, you probably won't know it and you'll be totally convinced that you are delivering the performance of a lifetime.
I am reminded of something soprano Maria Callas once said when an interviewer asked her about her emotional state on stage. It was his impression that Callas totally involved herself emotionally with the character and threw herself completely into the role. In other words, that she GAVE IT ALL.
"I never give it all. You cannot do that when you perform. It may seem to the audience that I am giving it all but believe me, I always have one eye on the conductor and the other on the tenor!"