Mistakes are inevitable. Decide before practice that every mistake will become a cue to reset rather than a reason to get frustrated.
During:
After a mistake, acknowledge it, make the correction, and move on immediately. Don't carry one mistake into the next repetition. Let the mistake go and refocus on your next effort.
After:
Did today's MindRep help you? How did today's MindRep help you? Do you want to own it and make it a consistent part of your training?