Just Play It
There's some lessons about performance that are hard for every performer, not just the writer and readers of this blog, it's everybody, every single performer keeps having to work on building these mental muscles, but, you can't flinch. Even if you're all by yourself in a subterranean basement, you don't want to throw your hands up in the air and yell, "Curses, another blasted mistake!" Seriously, when you make a mistake you can't let it be paramount and big, and then, you're playing for cleanness and clarity, and, of course, we do that, but not primarily. Playing is many more things than that, that's one of the great elements of playing, that you have to attain it by working and getting it, and it's freedom that leads you to that, and freedom is gotten by repetition and keeping good habits going. And the habit of flinching because you're thinking "Oh, I've made a mistake, now I've ruined the piece," or thinking about why you've made the mistake, and pretty soon you find you're making a few more because you're distracted and aren't concentrating on what you're doing at the moment.
Don't worry about having to play it "properly," just play it. Learn about spontaneity, and believe in it. Make it a part of your striving for excellence. Your playing can be very fine, you've worked long and hard on a certain piece and know it thoroughly, but every time you play it again there's going to be a difference. No matter how much you work on a piece it will never always be the same. It's important to enjoy [See blog, Having A Spec]. It may help to remind yourself that all you're wanting to do is provide some beautiful music, and that, whatever happens, no one's life is at stake. As for accuracy, it will come to you. It's like a cat. If you call your cat, she disappears. If you don't call her, she's right there. It comes and visits you if you leave it alone. When you want it, it's harder to attain, and it hides from you. So, don't bother to reach for it, just work, and play, and concentrate, and form good habits, let go of that perfection thing, and stay with the moment.