Ugh, just ugh. Disgusted with myself.

Don't give up! It's just ONE slip and you can pick yourself up and move on at any moment. It'll be so worth it. Knock yourself out of the fugue state, get some paper and a pen and out together a list of things you KNOW you manage to stick to for the next couple days. Even it's lean cuisine meals and go do some shopping and try to stick with it just for the next day or two, and then try again! It'll get easier!