Mine was a one-two punch.
Of course, I have always wished that my weight would magically disappear. I made vague motions in the general direction of dieting/counting calories/not eating after 6pm, but none of it lasted more than a week.
The first punch was that I had to go to a job interview. So I needed to find a nice shirt and tie and pants. I've been a college student for the past 3 years, so I really haven't had any need for anything but jeans and a t-shirt.
I tried on pants and none of them fit me right. I hated I had to look for the largest size and then it looked incredibly baggy on me, though I struggled to button it. Then the shirt was ridiculous, and I had to tuck it in and it was blue. I looked similar to a blueberry on a stick. I hate shopping for clothes.

Then I was at the doctors office, which I haven't done in a while. They took me to the scale and I weighed. I saw my weight that day and said, THAT IS IT! I left the docs office and went immediately to the store and bought (the wrong) hamburger patties and pork rinds.

In regards to theme parks. I totally know the feeling. Having them shoehorn you into the seat and then being terrified that they didn't latch it all the way. Soon I will go to Disneyland again and not have to worry about any of that...I can't wait.