This is my elevator door.

I go out of my way to keep it open for you if I see you come in the lobby after me, are pausing to check your mailbox, or are moving slowly because you're carrying a heavy load. So when you know I'm close behind, or when I call out to you to "please hold the door" as it closes in my face, I think you're spectacularly inconsiderate.

Tighten up. Courtesy is contagious.