In his book Effortless Mastery Kenny Werner introduces this image of learning. It's at the end and a lot of people have missed the fact that this is one of the greater points he makes in the book.

In order to really master something you need to work at it using what he calls "the learning diamond". It has four corners, or four points. One is at the top and can't be taken away and that's "play effortlessly". The other three are "play the whole piece", "play fast (or in tempo)" and "play perfectly".

Of these three you can combine any pair but doing this you need to omit the third part (or you will probably not play it efforlessly and thus you'll defeat the purpose). So, in other words, when you learn something new you can:

* Play it effortlessly, in time and perfectly but not the whole thing.
* Play it effortlessly, perfectly and play the whole thing but not in time.
* Play it effortlessly, in time and the whole thing but not perfectly.

The thing to observe when doing it the first way is that it may be a really small part of the piece you can play in time and perfectly and still do it without any effort. It may be as little as one or two notes.

The second way of doing it isn't very complicated to understand. Play it perfectly and without any effort as slowly as you need, not worrying about keeping time.

The third way of doing it has a therapeutic effect. You will get a feel for how it is to play the piece in tempo by playing it in time and all the way through but not perfectly. Still without any effort.