Sometimes the only difference between a good and bad day is how much water we were able to drink. Seriously, we forget how much hydration has to do with simply feeling good—until we're dehydrated and that brain fog, irritability, and fatigue hit us hard. Drinking water is the No. 1 thing we can do for our comprehensive well-being, but why does it feel so challenging to do something so simple? Because unless hydration is a bona fide habit, it won't stick.