As I remember, In Gerson's book, he discussed the 95-5 rule. Basically, you allow yourself 5% for some indulgence. I don't think that my indugences have come anywhere near 5% of my diet, though this past Christmas & Thanksgiving, I did eat some food that I would not normally eat. My rule is on those few and far between occasions that I indulge, it is something of exceptional quality and taste such as my niece's homade cheescake (Christmas).
I have managed to maintian reasonable protocol and diet even on vacation substituting Kyogreen powder for juice, and keeping the other things mostly the same.
IMO, there are several natural protocols that can resolve cancer, but for any, discipline and 100% commitment are essential.