The Tunnel by Ernesto Sábato:
I watched out the train window as the train sped toward Buenos Aires. We passed near a small homestead: a woman standing in the shade of a thatched roof looked up at the train. An opaque thought crossed my mind: ‘I am seeing that woman for the first and last time. I will never in my lifetime see her again.’ My thoughts floated aimlessly, like a cork down an uncharted river. For a moment they bobbed around the woman beneath the thatch. What did she matter to me? But I could not rid myself of the thought that, for an instant, she was a part of my life that would never be repeated; from my point of view it was as if she were already dead: a brief delay of the train, a call from inside the house, and that woman would never have existed in my life.