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His rationale is if you train your mind to stop and start over every time you make a mistake in practice that's exactly what you'll do in the field.
Thoughts?
There's certainly some validity to this concept.
I can't begin to remember all of the training or qual drills where someone encountered an unexpected occurrence, for whatever reason, and either paused or completely stopped. Not the optimal reaction for a real-world situation.
There was this one day when I was running a very experienced guy through a multiple threat/non-threat scenario which required movement.
The first armed threat target was right up in his face, requiring an off-hand blow to create time/space for the draw/presentation and a specified number of shots fired (following instructions under induced range stress). The target was free-standing (steel base).
His off-hand blow actually knocked the heavy target base over, briskly and hard enough so the threat target slammed onto the ground. Nobody else had hit it anywhere nearly as hard and caused that to happen. His reaction?
He rapidly fired the required number of shots into the downed threat's COM and instantly moved off to engage the remaining threat targets. In response to the quiet looks a couple of us (instructors) working that scenario gave him, as he was returning to the beginning position after he'd ID'd and engaged all the remaining threats, he quickly said that the armed threat he'd knocked over had still been holding and pointing a weapon toward him.
Training really can work, at times.
FWIW, it's when people start coming back after being involved in actual shooting incidents, telling you that the training had worked for them, that it starts to make it seem as though your efforts are having some practical effect.