You'll hear lots of horror stories, mostly from people who've never been on a diet in their lives, let alone the Cambridge Diet...
Ignore them. The first week is the worst, but only because you need to get yourself into ketosis--which is a bit of a trauma for the body. You'll feel tired and maybe a bit lightheaded--but it passes, and it certainly didn't stop me from functioning. I seem to remember from your earlier posts that you're a teacher? If you're worried about feeling lousy for a day or two, I suggest that you perhaps start on a Thursday, so that by the time the 'rough' bit hits, it's the weekend and you can just go to bed!
But it may not affect you that badly at all--it depends on what you're eating now. If you gradually decrease the carbohydrates in your diet for a few days before starting Sole Source, it almost certainly wouldn't be such a shock when you start. Don't go on an 'I'll eat everything tonight because I'm starting CD tomorrow' binge beforehand--you'll be asking for trouble, LOL.
I used to teach, so I know how tough it can be to keep going in the classroom--but by week 2 and 3 you'll feel much better--and you'll be a stone down by then anyway--so long as you stick to it!
Like SoonToBeGorgeous, I haven't actually had any lapses, so I can't tell you about how hard it is to get back on the wagon. All I can say is
tell yourself you're not going to cheat! From what others have said, it's tough to get started again--and why would you want to put yourself through that first stage again, over and over?
Taking a day off the diet isn't really a realistic option on this diet, so if you think you're going to struggle to stick to it over the next few weeks (Christmas meals, etc.) then you might want to think about how you'll cope with saying 'no'! (and when you want to start...)
But--if you're in the right frame of mind (and I'm not sure if you are, given you're already asking about not sticking to it religiously
) this diet really works!
I love it--and personally I've found it the easiest diet I've ever done. 2 stones off in six weeks--and probably still time to lose another one before Christmas. Almost everything in my wardrobe is now too big, LOL.
Anyway--gosh, long post!--all the best with your decision!