Sa tu dirgha kala nairantarya satkarasevito drdhabhumih I.14
Practice becomes firmly grounded when well attended to for a long time, without break and in all earnestness.
I refer back to this sutra all the time! I found I really understood the idea of "practice" when I stopped "doing" Yoga randomly, whenever, dropping into a class here and there and began a regular practice with the same teacher, every single Monday and Wednesday of the week. It became firmly grounded, I attended to it for a long time and was extremely consistent. This was when I truly began to notice my progression in asana, first. Then I noticed my progression mentally -I got passed the part of boredom, mind wandering, feeling like something was too hard or painful -I got passed the citta vritta -mental modifications. And as always, take this idea of "practice" off the mat...there are so many things in our lives that we want to work on...we can't expect an immediate result. These things we want to work on, they come with practice!