Stop obsessing about your hands, specially before a performance. They're cold, they're sweaty, they're sticky, they're dry, they're shaky- you've played with your hands in all kinds of states when you practice with no problem. It's usually the nerves that make you extra aware of how your hands are feeling before you play, it's panic looking for reasons to trip you up.
After a concert, a woman asked Joseph Hofmann how he could possibly play so well with such small hands. He responded: “Madam, what makes you think that I play with my hands?”
Forget your hands; practice is for your mind, not your fingers.