When I started played, I had no problem keeping my thumb on the back of the neck, in most situations. As I've progressed and began learning new songs, and building up my skills, I've noticed my thumb is getting "sloppy"; I put more emotion into songs, and my thumb ends up "rocking out", depending on what Im playing at the time. I've never had any kind of pain in my wrists, and I play on average 2 - 3 hours a day atleast. Is this really a bad thing; that my thumb is moving and reacting to my playing? When I force myself to follow procedure, my playign becomes.. stilted? It just doesnt flow right, and I even have trouble really laying it down.