There are 2 methods for getting over performance anxiety. I've used both but recommend the second - I'll explain why:

1. "The bulletproof musician" is where you get to a place where you focus and shut off all external forces. The way to do this is practice the same passage over and over in the same style, same phrasing, etc. where you develop the "muscle memory" to be able to play the passage at any given point (even when emerging from sleep). This method was used a lot by the Soviet musicians back in the day. However, if your mental focus cracks and you become aware of the audience during your performance, it's game over.
2. The second method is constantly practicing in front of an audience to the point where your brain can't differentiate between practice & performance. This is harder to achieve (and a little more terrifying in the beginning) because there are suddenly people in your practice session, but this is probably the most valuable reason I use the Tonic app. The result is when I now walk on stage, I have the feeling like everyone's here to listen to me "try things", just like I do in the Studio.

That feeling you get when you wish you tried different things right after they happen? Yeah, it's possible now which is pretty cool.