Most of the time when the number went the wrong way, Dad knew why. One day, it was three vodkas. Another time, too many carrots. One of my favorites: "freakin' lasagna." And seeing the number edge upward motivated him to make small changes day by day.
The only way to get away from its yo-yoing, confidence-sucking and confidence-boosting pull is to limit your time with the darn thing. And find a deeper and more real and stable sense of power; one that doesn't have a darn thing to do with how much we weigh.