I find that the minute you stop focusing on yourself and 1. realize that this is not brain surgery and 2. think about the words and the "scene" you are in, you may still be nervous (and you should be) but it doesn't affect your performance as much.
I do say that if you are not nervous when you perform you should quit because it means you don't care. But those nerves can sometimes be distracting if you aren't fully immersed in the song and your emotions and getting the message out there.
Or as my mother and her mother used to say "Just make your Bow Go".
The story goes like this: My mom is not only a lovely singer but also a violinist. And her mom was a local piano teacher in Duncan Falls, Ohio. Even though her mom was not an "degreed" teacher, her words of advice to her daughter (my mom) who was so nervous one time in a recital that she was shaking were, "Just make your bow go". And my mom did. We still say that to each other and remember Grandma when we do.
So simple...just make the bow go. Take a step. Open your mouth. Breath low. Sell the song. Take your pick of simple ideas that you can use as a mantra to get your nerves in perspective.
The only other option is to quit. And is that really an option? Push through the fear and just think about the mission and not yourself. I need that advice now too because the "fear" of this big event, May 1st, is sometimes overwhelming.
Make my bow go.
So whatever your fear is, dance with it and keep your "partner" in perspective.