Why am I so self destructive?!

Why do I always do it to myself?
Hungry for lunch and I stop for the all you can eat buffet at Pizza Hut.
It's not that I am going to make a pig of myself and eat more than I need. It's that I know the food is gross, yet still something deep inside of me say stop.
Now all of you getting ready to pass judgement- you've been there. How many times did you eat at an 'all you can eat Chinese buffett'? How many times did you start off with a salad thinking "well this is healthy (even if the lettuce is rainbow colored)" and finish your meal with a few trips to the soft serve ice cream bar covering that chocolate volcano brownie thing?
BTW- off 95 in western CT there's an American-Italian-Chinese Buffet that serves great Baklava and is owned by some Jewish guy.