Well, not that i’m anywhere close to your levels, either of skill or embarassment on stage, but here’s my story from when i had my first and nightmerish time on stage.
Our band was rehearsing in a small studio and for the first time we were actually doing pretty well.The drummer, during a pause throws in the idea to participate in a small gig at a bar we all knew.There would other bands like us (which meant tottaly unskilled ones) he said and it would be cool…

Well what he said was slightly off, as we realised in terror that the other two bands playing were something like underground stars with their own audience and even a groupie or two!!
Eventually we got on stage, in front of a completely surprised and drunk audience who thought that the gig was over….My face went through numerous colour alterations and i ended up staring the pavement all the time while my stomach was somewhere in the front raw begging me to stop.
The singer came to me several times asking what was the next verse!!!!
The bassist was the only one who was ok, but the drummer was constanly losing the pace and songs were like slowing down and speeding up all the time…
But the worst was at the end when we decided to play something easy and went for Punk Rock Song from Bad Religion: Total disaster!!!The drummer went on a rampaging tempo that didn’t let the singer take a single breath between verses and it all ended up on a mix of applause and laughter….gosh, at least they were nice with us and didn’t throw us anything!!!!