Another one of those "do's" that have no scientific foundation. There is no magic in deliberately consuming 64 ounces of water a day it is one of those truisms which have no factual basis. Drink when you are thirsty, you get water from a variety of sources from the food you eat. The point to remember is when you are thirsty drink do not sip, I suggest at least 8 ounces but recommend 16 ounces at a thirst cue. The colour of your urine will indicate if you are under hydrated or over hydrated. dark is under, pale is over, bright yellow is fine.