Hi - I have had this same conversation with my CDC and her advice to me is what I will pass on to you.
When struggling with the diet (which most of us do from time to time), don't make yourself really miserable that you end up packing the diet in completely and returning to your old eating habits or eating something that does not fit in with the diet.
You have chosen to do CDC and make certain changes in your life; no-one is making you do this, it has been your choice. What you decide to do when feeling really miserable and struggling, again is your choice and no-one elses.
My CDC has told me not to make myself unhappy (especially to the point of almost crying as I have been previously), instead have an extra shake, soup or bar. Or if that is not going to cut it, then have a light meal of chicken, fish etc and veg or salad. Try not to have any bread, rice, potatoes, pasta etc as this could instantly add pounds; but the other stuff should be ok - it may slow your loss down a bit, but shouldn't affect you drastically.
The point is, if you choose to eat a light meal, then plan it and choose to do it with a positive attitude. You will not have 'cheated' or failed in anyway but will have simply made a different choice that day and should not beat yourself up for it. If making the choice to eat with a negative attitude then you run the risk of eating foods that will bring you out of ketosis or coming off the diet completely.
So keep your chin up, and remember you have to look after your mind and emotional wellbeing on this diet as much as yourself physically, so if at difficult times, you choose to eat, not eat or have an extra CD product, then you have simply made a choice that is all. You have not cheated and have not failed.
Check out a previous thread from KD regarding taking a journey and stopping off to visit a relative - she puts it so clearly (she's a wise one is KD). If I can find the thread then I'll bump it up for you.
best wishes
Julie x
p.s have just found the thread I'm talking about and have bumped it - its on the main CD forum by KD and called "who is the better person".