No offence, but that sounds pretty naive. Pre-gig fears (for me) are nothing to do with being confident that I wont mess up, and playing a good gig is only 50% skill - at most - anyway. It's not like a talent show where you just have to have a good voice/play the right notes and that's enough, it's a performance where you have to leave the audience thinking you were awesome. Not to mention the added nerves that come from playing your own material to people who are (probably, at this stage) unfamiliar with it and will be inherently critical.
Which is why I, like most other people here apparently, have a couple of drinks. Not talking false confidence levels - just enough to calm your nerves.
If it's a worry of your charismatic performance but not your skillful performance then it's a matter of being able to just not give a hoot about the opinions of others which is something you really can't get rid of without something to dull your mind like alcohol. You can prevent yourself from thinking too much about your audience before you just have to be there playing by doing something to distract yourself from the show like play cards or play some specific melody with your instrument, but you're still going to be left a little worried as you get on stage unless the pace of the performance doesn't allow you to spend time worrying about anything else than your performance.
I may be a little naive on the subject since I've always been one to put myself in the spotlight since I was a kid but a common theme with me is simply to psyche myself up into thinking I am awesome already. People pick up on your emotions and if your goal is to have them think you were awesome then you yourself have to think you are awesome, and before you hit the stage. Just best not let it go too far and act like you are much better than you are, just acknowledge your own skill and act accordingly.
I'm still not fond of drinking before performance, becoming reliant on something to dull your own mindset to be able to play is just a little sad, you'll never truly get past stage anxiety if you never allow yourself to be hit by it full force and if you don't allow yourself to get used to it and then past it. I'll get a lot of heat for saying this but I think it's weak, it's avoiding your problem, not taking it on.
I agree with your point here, there's always that worry beyond your skill and proficiency that's simply the audience itself, strange business for performance based activities/careers as it can fall down to the taste of audience members alot of the time. Currently worrying about completely ruining Black Sabbaths Paranoid for the older pub goers!
Oh taste is to the audience, if you're going to take work that people already know and change it, then it doesn't matter how well you play, there may always be someone who doesn't like it just because you did change it.