You'll do fine!
I've been three days off of my 29 day fast, and it's been great. I've learned so much about my body and, even by eating healthy salads and stuff, you can still find that you are eating too much! I think the great thing about this fast is that it really teaches us how our systems were over-loaded before, and that there may be wisdom in this theory of eating less for longevity. I find that I am now wanting to learn to eat smaller meals so that I can maintain that great feeling I had while on the fast.
Regarding old habits, just think of it like a member of AA. Everyday, man...gotta dedicate yourself to not turning back every day. It's just like the fast itself: It just takes one split second decision...the one that gets you off your ass and into the fridge... to knock you off the wagon.
But the good news is that, if you plan well, and make your own lunches, dinners, etc...never having to search for something to eat on the fly, you're half way there. On top of that, every day that goes by gets easier. Just remember the split-second rule and never let it happen to you. It's surprising how much easier it is to resist temptation than it is to deal with yourself after you have given in to it.