At what point would you say that you “knew” a piece of music or an exercise? Unfortunately for most students it is when they have played it correctly…once. I used to hear it a lot. “I already know this, can’t we go on to something new?” It is frustrating because most times you know that they don’t really “know” the piece at all. They just got it right once or twice and now want to move on.

In my opinion you should not stop when you get it right, you should stop when you never get it wrong.

It is a subtle difference that was hammered home to me about 10 years ago when I had a one-off lesson with my original drum teacher. We had kept in sporadic contact over the years and when he offered me a couple of hours of his time for a lesson, I jumped at it.
I was a bit put off though when he dragged out one of the most basic drum textbooks from my bag and turned to a very simple exercise that really only had three notes in it. “Bruce, I already know this.” I said.
“Do you?” was his reply.
“Can you play it for me with a swing feel?”
“Can you play it left handed?”
“Can you play it with your feet?”
“Can you play it with your feet left handed?”
“Can you make a fill out of it?”
“Can you play it on top of an ostinato double bass drum pattern?” etc, etc. On and on we went for nearly two hours working on an exercise that had three notes! By the end, I was convinced that I knew the piece better but nowhere near fully. It completely changed the way I looked at my practice techniques. I was also very hesitant to say that I “knew” something.

Don’t be so keen to get to “the next great thing” until you are really sure that you know the stuff you’ve already worked on. I don’t mean that you just keep playing the same crap over and over either. Vary it. Do it slow, fast, backwards, left handed etc.
You will find that even some of the simplest patterns can be turned into quite complex exercises that require a much higher level of skill than you first thought. It is also a great way to get excellent value out of your expensive textbooks.