When politenesses collide. As I was coming back from lunch, I saw a man ahead of me get into the elevator. I was just far enough back that I figured I'd hold him up if I tried to rush (the elevator would have already started to close by the time I got there), so I dawdled a bit so that he could politely close the elevator door without looking like he was closing it in my face.
→[More:] Then I saw the door was staying open longer than I had anticipated, so I went over, and when I got there I saw he had been holding the door for me.
Poor guy. Done in by my overthinking.