I have no idea about juice fasting so can't comment on that. From my experience with fasting I think you need to focus on not only the fast itself but an equal amount of days past the end of the fast. So if you intend to fast for 10 days on water only you not only have to focus on not breaking that fast but also when you do think about the days following the fast you focus on breaking the fast properly. Fully plan ahead a gentle return to 'normal' eating, allowing the body time to function again as a food processing machine. Our bodies don't switch from fasting mode to eating mode that easily, it all takes time. So plan for the time it takes to complete the fast and to recover for an equal amount of days, or if you plan to go straight from Water Fasting to juice fasting and not break the fast at all between the two then plan for the whole water-juice fast time and whatever amount of time they recommend for refeeding after that juice fast. After that length of time you would still want to start off with gentle, soft raw foods and make sure the body is functioning properly on those before adding any cooked food at all.