For me it's been a few things; one of the big realizations was that my DH doesn't have to go along with my diet, he's responsible for his own health. (A long story).

I'm tired of sitting on airplanes for 10 hours in huge discomfort, with trays that won't come all the way down because of my stomach. I'm tired of feeling like crap. I'm tired of limping because of sore back...sore knees, etc. I want to wear shoes that aren't slip-on, I want to be able to try on lace-up runners in a store without risking toppling over like a damned weeble.

Voo, your first sentence about watching the scale go up was amazing to read....I did the same thing. It was weird, and I still don't quite understand why I felt that way. I lost about 50 lbs about a year and a half ago, and I'm shocked that I've only regained about 8. I've been lucky, because I've not been careful at all.

Now, at 50+, I have the feeling of running out of good luck. I've turned a corner mentally, time to smarten up. For good.