About 6 or 7 years ago I stopped smoking, and I couldn't find any more excuses, and got myself a gym membership. After being scared to actually go to the gym for about 3 more months, once I took a deep breath, and made my first visit.
After 15 minutes I almost died, I was so exhausted. I was very disappointed, and went to the burger king next door. I paid for my order, and when I got it, I got disgusted by myself. I threw it to the trash without touching it, and next day I went back to the gym.
I continued doing so for months, until I eventually got a 4-pack (I never got to a 6-pack, grrr).
And at this point an old colleague sent me an email, with a job offer, out of the blue.
The job was very good - the guy knew that I would love it, and I did, too much actually. I pulled 16 hours long workdays (which I enjoyed, mentally), started to eat crap again, and in a year I couldn't button my shirts.
At this point I quit - I felt that my physical health was deteriorating, my body was begging to stop. It took over a year to get back in form again. My job is worse than it was, but I couldn't control myself when I was having way too much fun.