Imagine this scenario: You’ve just come out of a firefight, exhausted but unscathed. Coated in sweat and dirt, you reach for your standard-issue canteen for a swig of water — or, if you’re lucky, something a bit stronger. But hot damn, you’re fucked: A piece of shrapnel or spare bullet has punctured your canteen, spilling your water or whisky onto your uniform. Your thirst will go unquenched.
Benjamin Franklin nailed it when he said, "Fatigue is the best pillow." True story, Benny. There's nothing like pushing your body so far past exhaustion that you'd willingly, even longingly, take a nap on a concrete slab.