Mess up on stage? Keep going. The audience never saw the plan.

An audience has no reference for what was supposed to happen. They hear what you give them, and a wrong note only becomes a mistake when your face announces it. Stopping, wincing, apologizing, all of it hands them information they did not have. Performers who seem unshakeable are mostly just people who kept moving.

Practice recovering, not only playing. Fumble on purpose in rehearsal and continue without reacting, until continuing is the reflex. On the night, if something slips, go straight to the next thing and let it stay a private event.