I'm not sure if this story will help, but for what it's worth:
I had to go to the dentist today for an extraction, which I knew was going to be particularly difficult, so as you can imagine I was not very relaxed.... However, I was lying in the chair and the dentist was just prepping up, when Solveig's Song came on the radio. I found myself tapping the beat with my finger and I was really enjoying the music and didn't want to miss it when the dentist came to start. So I asked him to turn it up a bit, and then I made a conscious decision that instead of paying attention to what the dentist was doing, I would focus completely on the music, so I asked him not to talk to me this time about what he was doing.
And it really worked
Instead of being a nervous wreck, virtually clenching my fingers to the bone, my hands were completely relaxed as I beat time to the music. When the drilling got a bit too loud for me to hear the music, I switched from "listen" mode to "play" mode and started playing one of my G3 pieces in my head. I had to start humming it in order to concentrate, but I thought, well why not - at least the dentist has got a nice relaxed patient here
So there I was, humming away and beating time to my G3 piece and concentrating on the dynamics, happy as a lark, while there's all sorts of mayhem going on in my mouth
Anyway, the moral of this story takes me back to something which cropped up in a recent thread started by Sarah-flute:Nerves, Acting, Feeling/appearing Confident
Sarah-flute talks about getting "lost in the music" and going into a zen-like trance of being completely absorbed. I connected with that concept at the time and described it as putting the music first instead of yourself and your nerves.
It's all about focussing on something else other than what's happening to you personally. So in my case it was the music I was concentrating on to take my mind off my dental treatment, and similarly in the case of Sarah-flute's performance confidence, it was a matter of realising that the music is more important than yourself.
So I'm not sure if any of this is of any help, but if I can do it at the dentist for an extraction, it must be worth trying for a music performance!
Incidentally the dentist had heard me humming my piece even though I was trying to do it very quietly, but fortunately he played the trumpet before family commitments took over so he quite understood
And it turned out that Solveig's Song was one of his favourite pieces to play