He knows there's a shot for him yet, after all, but in my mind I'm thinking "wow, he's so nice and such a good friend, and mm, wouldn't it be neat if..." Anyway, I finally got frustrated enough with my then-boyfriend's emotional distance that I broke up with him and rebounded with the new guy.
(Technically I was going to break up in person but I got a "yeah, so, I'm gonna spend Thanksgiving with my roommate's parents, see ya later" note from the then-BF, so I figured screw that, and IIRC started up with the new guy before writing the "Dear Jerk" letter.
I'm also talking with a mutual male friend about our respective dating partners and whether he and I should/shouldn't break up with them.
Unbeknownst to me he's feeding this info to the other guy, who's continuing to be friends with me but isn't above acting mildly flirty.
I was also having an affair with my old boss, a much older married man who loved me and whom I loved, but who really was in no position to be with me full-time.
Since neither relationship was really appropriate for a nice young woman like me, my co-workers fixed me up with the old friend of the fiance of one of them.
The day after our first meeting, I saw the old boss and we spent the night together, but he told me then he knew I was going to marry this guy (even though I wasn't overly enthused) and he was right.