When I was playing pool in college, I took a road trip with a pretty well known road player at the time. I was hitting balls by myself on a table and he walked over and asked me what I was doing. I said, 'practicing.' He said, 'you're destroying your game!' He explained to me: you should never, ever hit balls or play just for fun. The only time you ever even pick up a pool cue, is when you're gambling (called being in action). Being in action focuses the mind, requires complete attention, and is an entirely different level of discipline than 'practicing' when there is nothing to lose. This playing for fun practice only causes a lack of attention and bad habits. I took his advice, and my game improved dramatically in one summer, even though I was playing far less pool in terms of hours. And my enjoyment of the game increased. The same is true of music, I always try to play with a clear objective, something to lose, with complete focus, never just noodling. It's far more rewarding.