We talked about how our muscles require lots of reps in order to become stronger. Same with practicing music...we can complete a lot of reps to help with muscle memory and to become stronger players. Playing through a difficult measure only one time is like doing one push-up calling it an effective work-out.
I try to do lots of reps in class and encourage students to aim for 10 times perfect each day on every exercise to become PRO players. This has been helpful for students first learning D string notes. They have to fill out this tracker at home when they practice: