I slept with my best friend's brother and it was the best time of my fucking life, but...it could never be anything more than one night.
For one, he hates me. (And I hate him.)
Second, I'm married. (Yeah, that too.)
And third, he knows me. (He really knows me.) As in he knows where all the bodies are buried, and he's been keeping my secret for years. And while I'm not ashamed of my past mistakes, he's still holding them against me.
I don't know that he'll ever get over it... (Right, I know. He's never getting over it.)