then again, there are the hardy folk who like a challenge, and start on a full moon, which is an optimum time to take a (Himalayan) crystal salt bath, and *absorb* the minerals, just to top up; as well as being a good time of heightened awareness, all around. But people generally tend to go to excess, at the *full moon, (and all times) so with water fasting, *it would suit the renunciate-type, and not the sensualist.
But at full moon the brain is heavier, holds more liquid, and this, among other stuff, can make some people feel whacked.
Getting drunk on a full moon -also- is always a bad idea, as the body holds onto everything, more deeply.
Don't beat yourself up. We are deeply conditioned to NOT move past those first three days.