Insta-Regret

Regretting something almost immediately after it happens. Usually leaves you wondering why you did what you just did.

Often occurs after text messages, sent e-mails, and that last drink you shouldn't have had.

"You probably shouldn't drink any more of that tequila, I bet you'll insta-regret it."

"Shut up, don't tell me what to do! (takes a swig) ...Ahh crap, I feel nauseous."