I used to weigh myself two times a day all through college and until I had my first child -- and began again after my second was born. It started because the daily dorm breakfast of buttered cinnamon toast (three slices) ended up pushing on the seams of my jeans. When I finally got on the scale - it turned out I was up 8 pounds - Never had a weight issue before and now I was freaked.
I just bought a brand new digital bathroom scale, so naturally I step on it every time I'm anywhere near the bathroom in order to watch my weight fluctuate. A mammoth salad for lunch? I'm up two pounds! A pleasant ramble with the Yorkie-poo? They've gone! Dinner at my sister's house? They're back! But by tomorrow morning, they'll probably be gone again. Or not.