It's a tricky one to answer this as there's a bit of me that's still scared I'm going to fall off the wagon, even though I've managed to keep going for 24 days now.
Like you, I managed to do CD 100% for months on end and lost 5 and a half stones. Then we went on holiday, and well, I ended up being tempted to eat - and never managed to climb back aboard successfully. It's taken since July last year to get myself back to this point (and I thought I'd cracked it in January - managed 3 weeks then and still fell by the wayside, doh...).
So why do I think I might make it this time? Well, I just reached a point where I realised enough was enough. That I didn't want to be doing Cambridge on and off forever - I wanted to do it one more time and then get on with the serious business of learning how to maintain, developing a new and healthier relationship with food.
So I decided that I'd have to commit 100%. That I wouldn't pretend that nibbling at bits of chicken was a legitimate cheat. Basically, I set about restarting by doing exactly what I did that first time - following the diet to the letter, having exactly what I should have and nothing more (well, okay, apart from the odd sneaky Coke Zero - it used to be legal and it didn't do me any harm the first time around
). Oh, and the one big thing that seems to be working for me - having no idea how much weight I'm losing. I've agreed with my CDC that I'll only weigh in once a month. That way, I have no idea whether I've lost weight on a day to day basis. I'm trusting in the diet to do its job, not trusting in my scales - because scales lie!!
There's no magic answer, I don't think. For me, it boils down to the simple truth that I don't like being overweight - and doing CD is the fastest way of getting to where I want to be.
All the best with your restart. You can do it - you just have to believe in yourself and the diet. CD works. Fact.