Allen Paul says to maintain your poise:
The moment is usually brief, but it feels like it lasts forever.
It is the moment in a performance where something goes very, very wrong. Far from a missed note, or a mistaken melody, it usually involves a musical issue that is painfully obvious and regrettable. The musicians are lost, the leader or soloist is confused, and the audience can sense or even see that there is a problem.
At that moment, some musicians let fear and frustration overwhelm their musical ability. Instead of processing how to fix the issue, they panic.
What do you do when panic threatens to destroy your performance?