This sounds horrible, but most of the time you will not play as well in front of an audience as you did in the basement. So what do you do about it? Sure, you work on your confidence and minimizing performance anxiety - that is material for several blogs. The other strategy is realizing that you will not play as well in front of an audience and accepting that. So, you keep improving and making your 100% in the basement better and better. That way your 80% in front of the audience is not only acceptable but very good. Audiences, in general, want to be entertained and unless you are playing for a bunch of musicians, they are not listening for mistakes (OK, that sounded a bit cynical). So give yourself a break, realize that you will make mistakes and come up short, but that is OK. You still sound good and you are providing a great show.
Dr. Michael Kearns
Musician, educator, husband, father, web designer ... my life is like a mosaic with each piece vying for my attention.