I have read that the "Thin for Life" research indicates that most ppl who lose weight & keep it off weigh daily. They don't necessarily respond to any fluctuation, but they do keep track.
I weigh myself at home every morning right when I get up. My official weight is on the balance scale at the gym. There's usually 3-5 pounds difference between the two -- I'm clothed at the gym and have been doing my day. I keep track of "new lows" with either scale.
Weighing myself this often has helped me become less neurotic about any given weight -- I have seen my weight fluctuate depending on the time of the month, what I've eaten recently, and who knows what else. I'm an engineer by training (which means I love data

), so that may have something to do with my approach also

.