Origin: The engagement is sealed with a diamond ring, and your female friends aren't actually any more attractive than they used to be; hence, the "diamond deception."
Guy 2: Thanks, bro.
Guy 1: How does it feel?
Guy 2: Well, honestly, these last few days I've been noticing how hot all my female friends are. But now that I'm engaged to be married, I'll never be with any other naked woman again!
Guy 1: Oh man... you're totally suffering from the diamond deception!