After a certain minimum level of required practice, it is not the amount of time one spends in music practice that matters, it is HOW one practices. Mindless repeats without a clear goal will only reinforce bad habits, and habits can be physical and auditory. Asking a student "So which sections do you think you need to work on and why?" will force them to put on their thinking cap and reflect. Adding "Where specifically did you hesitate and how can you solve this problem" will develop their critical thinking skills. To be engaged in Mindfulness in music: "Deep practice," is never boring. There is always a small goal to achieve. When it is achieved there is another small goal to set. Just one simple step at a time.
Yet there is a limit on how much “Deep Practice” human beings can do in a day. Ericsson’s research shows that “most world-class experts-including pianists, chess players, novelists, and athletes- practice between three and five hours a day, no matter what skill they pursue.” This is probably because “Deep Practice” would have drained our brain power, and our concentration would be diminished after three hours. Thus for younger students, if you are NOT mentally tired after an hour, then you did not practice very deeply.
If we were truly in “Deep Practice” we should also have the impression of continuing to rehearse the material we just learned while we rest. Students have told me that they dream about their music pieces after intense rehearsal sessions. Research suggests that when rehearsals are spaced out, the brain uses that rest period to consolidate that new information or skill and transfer it into long term memory.
When studying alone, it is hard to push oneself out of our comfort zone to get into this “Deep Practice” zone. Our brain likes to zone out and let automaticity take over. This happens to some of us when we drive and take a wrong turn because that is a turn we often took. Or we eat without knowing we are eating because we are reading, or on a phone, or playing an app. To be in "Deep Practice" is to do ONE thing at a time, but REALLY WELL.
Sometimes it takes an outside source, a teacher, a peer, or even an object, such as a random alarm, to help us realize that we were zoning out. Perhaps it is time to stretch? to check our posture? to REALLY listen?