I think if you're still in control when you "cheat," then it's a "flexibility" day. THe part I'd worry more about is the feeling fat and bad the next day - I'd try to guide the motivation to get back on track in a more positive direction (as in, this is exactly what the *plan* is... 6 days on, one day a little bit off...) If the cheating is bordering on bingeing... that's when (IMHO) it's bad.