I have no idea if the similarities in CJ's pattern of A's is of any help at all, but he did the EXACT same thing.
(Perhaps if you're reading CJ you could chime in?...I don't think he's around much here folks).
His first A started as a friendship, he knew he was unhappy, took it too far but realized after their first physical encounters that it was "wrong" and wouldn't help our M. (Which, I assume, didn't really occur to him before this???). But right on the heels of that rather rational and good decision, he "fell in love" with OW #2...the one he was ready to run off to.
I don't know, Sad. It happens. Do what you need to to process and work through these new feelings about A #1. I wonder if I'll ever need to do that? It's always been the lesser concern for me.