I come from the other end of the spectrum in that I was a good performer for a long time playing in a metal band, stage fright wasnt realy an issue , I was playing in front of a lot of people and other musicians and 'cuttin' heads'. I had a career , future and income, ridign on my abilities.
I've only gotten a sence of stage fright recently since my health has made it so hard to perform anything. My memory is shot so Im always forgeting lyrics , and my hands cramp in the middle of songs so I can't go on. And most people don't know or care that it is from disability and just asume I am inxeperienced as a musician and no good. It has realy distroyed my confidence and given me 'performance anxiety' knowing I can't play without making many mistakes or worse. It realy reared its ugly head when things got so bad I couldnt teach and couldnt even demonstrate to my students how to play things I was trying to teach them
so now I have the cringing apprehension to play for people or have them hear me playing, so I realy just play for myself and prefer to play by myself but if others are around to hear it that is their problem, they just have to suffer! lol
but luckily the uke is easy enough for me to play (at least basic stuff for short periods of time) to where I've gotten some of my confidence and enjoyment back playing music again.
I guess as soem say it comes down to a persons confidence in their abilities and how well they know the material. but a huge part is how you see yourself and how tied to your ego and sence of self worth (and survival if it is your career) your identity as a musician is. In most cases its not so much about how others are judging you as how you are judging yourself.
still the world is full of critics and people can be very cruel, just read some of the comments bandied about on youtube, some of it shocks me how awful and hurtful people can be to others. that alone is enough to give anyone performance anxiety! Luckily in a live situation you dont
usualy get people screaming out in the audience what a #$%$%^*#%^ you are but I have seen bands at concerts get booed off the stage.
I agree with the idea of doing charity shows and playing for seniors, and hospitials, for people who are appreciative and you are helping in turn. If you are bringing something good into someones life, there is nothign to fear.