I've never been able to talk myself out of anxiety, although EFT tapping has sometimes helped. I used to perform on stage too and pretty much always felt nervous beforehand. However it would nearly always go away once I started singing. Hopefully if you just go out and do the performance, even with the nerves, eventually it will get easier at least during the actual performing -- have to focus so much on what you are doing it's easier to forget how you feel. Best of luck!!