If you're a polite person, it's muscle memory to hold the door open for whoever's behind you.
I was leaving my university library through a revolving door, and I was reading something on my phone. This gorgeous girl was behind me with a coffee in one hand and books in the other.
As I exit out into the open, without even realizing it, I hold my hand back to stop the motion of the door. She walked right into the glass, spilling her coffee all over herself.
I panicked and ran.
I can never go back.