I weigh on Mondays as well for the same reason as Squeak. I actually weigh every day to stay accountable. BUT the Monday weight is the one that "goes on my permanent record".
Wiggle room is what got me jiggly. No use for it. If I can't "enjoy the weekend" without cheating on my diet, then I have more going on than a weight problem. Wait...I DO have more going on...that's WHY I have a weight problem.