It depends somewhat on where you live, but in the desert Southwest, carrying water might be in order. Just back from my morning walk; if I’d walked any further, or if the temps had been higher (ie, in a couple hours), I’d have needed water during the walk rather than now, after the walk.

If necessary I could have fixed this by using another of my essentials and just bought a couple quarts at the supermarket I passed, fortunately, that wasn’t needed.

11. Water.