In ancient China there was a doctor whose job it was to accompany the army to battles and to patch up the injured soldiers so that they could go back out and fight.
However he became quite distraught at seeing again and again over and over that the very soldiers he helped would die in battle.
He questioned whether being a doctor had any meaning or significance given that he was achieving nothing in his own eyes.
After studying with a zen master he came to understand the problem in his thinking however.
Whenever he started to feel those same thoughts again he would just say to himself "I do this because I am a doctor".
He needed to understand that there is no self or other. There is no subjective or objective. He was relating himself only to the situation. Everything is just the way it is. The situation is just the way it is.