Why not 1000 calories?

I am a psyched dieter! I'm currently well over 200 lbs and doing 1200 cal/day. I could do 1000 though. I dont because I hear it's too low but why? If I feel good, am eating healthfully, and taking supplements what's the problem? I know it couldnt go on forever because at some point I probably will feel denied and have to increase my calories in, but why not take advantage of my excitement for a few months? Educate me please.