You missed the shot, the cue, the high note. The next one is still coming. Get your head back in the song.

A mistake in a live performance costs you the next few seconds as well, if you spend them thinking about it, and those seconds usually contain something you could have got right. Dwelling in the middle of the thing turns one error into a run of them, because your attention is behind you rather than where the music is. The recovery matters more than the error. Another note is always coming.

Agree with yourself in advance what you will do when something goes wrong mid-performance. One breath, eyes up, next note. Practise recovering on purpose by making a deliberate mistake and continuing without stopping.