I am not nervous often, but recently I played solo acoustic at a friend's wedding and I had to sit thru the ceremony and then break into the 'recessional' piece. I started to flub it pretty badly and people could tell because the piece was Here Comes the Sun. This was a real bummer, but I just kept at it and no one said anything.

But...when you are soloing, no one knows what you INTEND to do. So, no matter what you do, pretend you meant to do it. If all you can muster is shaking hands, just play some long shaky notes and pretend you are really into it.

Bluffing works onstage big time. I once kicked my chord out of my guitar and finished a 3 minute song before I could plug it back in. I pretended to play the whole song while I was unplugged. No one noticed except the bass player. Even the drummer didn't know.

So, just fake it.