An emotional and mental phase that one experiences after he/she was crazily drunk the night before. As the name suggests, the person is very regretful of the things he/she did the prior night... and in most cases, he/she calls up his friends and apologizes for his/her behavior for the prior night. This phase usually involves a personal promise that he/she will never get that drunk again.
Guy1: Dude, I got really hammered last night. Did I cause any scene?
Guy2: You, fool. You puked all over Gerald's couch. I had to take you out of his house before he could find out and kill you last night.
Guy1: Fuck. That wasn't the real me, man. I'll never drink again.
Guy2: You're just in your "remorseful phase." Give it a week or two, and you'll be at it again.