I think it's more of a mindset above everything else.
For example, when I'm practicing or learning any new skill - or even the skills I excel at - I always view it as the perfect time to make mistakes. Not that I'm out to make as many mistakes as possible, but that I accept my mistakes as I make them, and immediately think about how I could become better so I don't make those same errors again and again. If I'm encountering multiple mistakes in a row, I know I'm in above my head and need to tone my learning down a notch and see where I went wrong previously. That might be what you're dealing with - if you're trying to tackle too much, too soon, you'll naturally feel frustrated. Gotta start with the basics and work your way up.
As far as actual performances - if you make a mistakes, best thing to do is keep on going. Mistakes can arise through nervousness, of course, but they also can arise from being ill prepared. So the better your practice sessions go, the better off you'll be when it comes time to shine.
Hope that helped a little bit!
