I've thought long and hard about it, and for me, self-sabotage comes from fear of success. Sounds weird, right? I've been losing and gaining weight all my life, and now to have broken the cycle scares me sometimes. I'm also starting to get more attention from others, which has always terrified me. Sometimes it's easier just to be invisible instead of being the center of attention. It's very strange to overhear friends and family whispering to each other about how great I look, getting jealous looks from other women and appreciative looks from men. It sounds like a dream come true, but for someone who isn't used to it, it can be pretty scary. Sometimes I feel like hiding under a rock.
This is just me, though. You have to do your own soul searching and figure out why you self sabotage. In the end, this battle isn't about food, it's about ourselves.