I notice that I advance when I practice mindfully, paying attention to what I am doing and what I am supposed to be doing. I break down problem areas in a piece sometimes just repeating the same few notes, or a phrase, over and over again until I get them right… Then I can assemble the pieces. To play a whole piece over and over again doesn’t work for me… I need to break it down into smaller parts and practice repetition on the technically difficult parts (for me). If I were to just play, I don’t think I would advance quite as well as I have been. When I have practiced until I have all the technical kinks ironed out, then I can put all the parts together and play.