Everything written after 9 p.m. local standard time (emails, texts, Facebook messages, etc.) must be approved by an objective party in order to prevent the sender's potentially profound regret the following morning.
Mike: I still love her, man. That's it, I'm sending her a text right now to tell her.
Aaron: Whoa there. It's 11:30, the Rule of 9 is in effect. Hand over the iPhone.
Alison: My boss is such a bitch. I can't take it anymore, I'm sending in my resignation right now.
Jill: Rule of 9; back away from the laptop. You'll thank me in the morning.