I used to have the same problem at my first live performances. What I tried to do was to stay concentrated on what I was playing, so as to make less mistakes.
It can be hard when you are trying to dance/jump/whatever not to make mistakes,but it can get used to.
You can also try to do that at home alone. Play standing up and try to do what you do when you are performing in front of other people, so as to get it perfect.
I would say the most important thing is to practice really really good what you want to play and try to stay as concentrated as you can on what you play during the gig.