Been there, done that - so listen to me well. Never ever feel guilty. Okay, you got off track - in the grand scheme of things, it's not that big of a deal. I'll tell you right now, you will always have days, even weeks like that - where you eat what you shouldn't, or don't exercise as much as you should. But it's not going to make or break you either way. You just need to pick yourself up and dust yourself off. It's never too late.
So, you need to stop feeling guilty. Guilty feelings just make you feel more discouraged. What you DO need to do is start working on eliminating tomorrow from your vocabulary. You may have had a bad breakfast, and followed it with an equally bad lunch... but that doesn't mean you can't make yourself a good dinner. And that doesn't mean you can't pop in a workout DVD or head over to the gym this evening. The more time you waste saying "tomorrow" and feeling guilty, the more opportunities you are going to waste.
It's hard, I understand. I've had several weight loss cycles where I've lost weight, and 3 months later had a bad week and gave up... gained it all back and had to start over again. This weight loss thing, it's as much a mental game as it is a physical one. I've been at this for about 9 months now. I still have bad days and weeks.... I still feel guilty sometimes... I imagine I always will, even at goal. And I'm sure you will too. But it's just like riding a horse. You fall off, you just gotta pick yourself up and get back on.
You can do it. Believe me, I've been in that place where I've felt totally hopeless before - if I can get past it, so can you. Send me a PM if you need a cheerleader or want to chat. I have faith in you!