Hope. Take a deep breath. Meditate...even better.
Tell yourself you're in control now, and you can always stop before it gets worse. I had to do this myself last night and sure enough I didn't wake up all groggy and bloated and depressed. Well, I was groggy, but that was because of not enough sleep.
You can always choose right now to start being good again.
Oh, and I just ate a fiber bar. Needed chocolate myself and that was the best choice