Part of it may be your subconscious devaluation of money. When I first move up to new stakes I tend to play well because I respect money more. When I get too comfortable at a level, I tend to call and make larger bets and play back more often to test whether people are just trying to make a move on me. I nice downswing usually puts things back into perspective. But, just recogniszing that you are doing so is probably going to help you address the situation.