Despite having moved from a third floor apartment to another third floor apartment (and having lived in a long series of third floor apartments before that), I keep stopping on the second floor, thinking that's where I live. I worry that I'm terrorizing whoever lives there as I repeatedly try to put my key in their door. I know it would freak me out.

Realizing my mistake I always say aloud to myself, "Oh wait, this isn't my floor," in a slightly louder than necessary voice, hopefully calming whoever is on the other side of the door.