My motivations change each time but I think they could all be summed up to one word. Control. I didn't realize it until I started seeing T of course; and she's never said word for word thats why I do it she just helped me become more self aware and that was the result. Very rarely do I do it as a punishment (in fact, I can only think of once that it was ever a punishment and really it was more that I was mad at myself). Usually it's because i'm holding on to frustration and occasionally because i'm overly tired and emotional and/or need some peace and quiet/distraction. In most of the cases, its relatively easy to stop. But I rarely make the choice to stop because in most cases I just don't think about it or brush off the thoughts. I can go a very long time without doing it and most often make the choice to stop holding back and "just do it"; the "just do it" part is the only thing T & I can't figure out though.