I find that one of the most difficult things to correct in a student is a propensity for stopping - both while practicing and while performing in lessons. Of course, anything that happens over and over again when you practice will be overwhelmingly likely to also happen when you perform.
Every one of my students, including those who struggle with briefly stopping to fix an error, know they are not supposed to stop. But telling yourself to not stop over and over again gets the mind thinking about one thing: stopping. To quote the great brass pedagogue Manny Laureano: “The human brain does not respond well to the word don’t.” His point is that we should always be thinking (and writing in our parts) a positive message and not its negative correlary.
Lately I’ve been taking a different approach to teaching the concept of always continuing with a performance, even one in a practice room. I subscribe to the Arnold Jacobs concept of always playing two horns - the one in your lap and the one in your head. The horn in your head should never stop because it never makes mistakes and never plays with question marks, always exclamation points.
The horn in your head should have the same autonomy over your playing that a conductor does. Imagine if Alan Baer made a mistake in rehearsal and cut off the New York Philharmonic from the back row in order to take another pass at the passage. Even a player as amazing as Alan would be unemployed quickly!
We are all capable of not stopping in rehearsals. So if we give the horn in our head the same respect that we give to conductors we will have no problem not stopping.