Well, let's think about the hand... The man can make his hand as tight or loose as he wants and move it as fast or as slow as he wants. This can be a very serious problem because he may now just be finding more satisfaction from masterbating than with actually making love with his girlfriend. Or..... There may be other issues here. Maybe he is thinking of someone else while he is masterbating. Maybe I'm wrong, but maybe he is homosexual and can't tell her.