A practice…

Is any consistent time spent on learning a skill where the success is measured by improvement not by complete mastery. 

If complete mastery is possible— it is not a practice, it is a task. When you treat a practice as if it were a task you work against yourself because a task assumes that once it is completed- the work is done. A practice is the work of returning to and refining a skill that will never be completed. And that’s the point. It’s not bowling.

If insanity is doing the same thing over and over expecting different results–

Than practice is constant effort, review and modification while expecting different results.