Drinkable tap water is easy to take for granted. At home, whenever I'm thirsty, I go to the nearest faucet without thinking about it. But, on the road, I've realized the importance of having an extra water bottle on hand.
For example, if I want some water in the middle of the night, I can't be sure that I'll be able to find a place to buy it. And if it's late enough that all of the stores are closed, I need to be willing to wait for the water to boil and then cool down to satisfy my thirst, which takes more patience than I'm used to.
At home, I have little idea of how much I drink everyday. But, when I need to monitor my supply, I've noticed that I do a better job of keeping myself hydrated.