Ah yes, I have the most interesting story. A few months ago I started a juice fast which I intended to carry out for 21 days. But starting on day 18 or 19 I started to get occasional headaches, shoulder aches, and I just felt really grumpy and tired. However I was so convinced I would stick it out. Besides, you aren't supposeded to end a fast early because those bad symptoms are a sign of the real detox starting. So... I held it out until day 20 (a Sunday). But I had some homework due that night, which I could not concentrate on at all (I couldn't stop thinking about my discomfort and craving for food!). So, feeling sort of crummy, I caved in on that 20th day. And even though you are supposed to start eating lightly, I didn't. I went ahead and had a 'big' dinner (for breaking a fast). It was all raw, but it was probably too much nonetheless. The entire next week I was overeating quite a bit (probably because my body felt like it had been deprived)... And to be honest, I don't think eating helped a lot that Sunday night, in terms of feeling better and focusing.
So... I really don't know what to say (lol). I can't say I regret breaking my fast, however I do admit that continuing the fast would've been the wiser decision- the whole point of it being to cleanse.
Furthermore, cleansing and fasting is supposed to be done when you are in mental/physical/emotional/spiritual peace. During a vacation, for example. So if you feel like you have a busy week coming up, it may not be a good idea. Too much stress on the body, you know? Or... find a middle ground with juicing/eating small light raw meals. Whatever works for you.
Hope this helped a little :)