Have you ever thought about how long a soldier lasted in a battle back in medieval times? Unlike what we see on television, some soldiers would just run out of steam and get killed just standing there or some would go to the ground for a rest in hopes of not getting killed while on the ground. After they rested, they'd jump up and continue fighting and the cycle continued throughout the battle.
Smart military leaders actually had a start and quitting time for their soldiers and would make deals with the other side to refrain from battle until the troops were better rested. They'd also use that time to remove bodies from the field. The strange thing is that many times soldiers from both sides would walk around the field together removing bodies. They had a mutual respect for the warriors who fell.
It's strange to me that people could fight the way they did and then do it again the next day like it's just a day at work. How did they keep themselves motivated day in and day out? Pretty amazing.