I think I understand it better. Actually, that describes my breakup with Raga, too. We needed to go in two different directions and for a variety of reasons that meant breaking up. I still love him and I'm sure he still loves me, but I've said goodbye to a future in which we'd be each other's primaries, because it just can't happen... Just like I've had to accept things wouldn't happen with some people who have rejected me. And while it doesn't mean I don't love him anymore, our relationship dynamics have changed for sure.
So I think I see how it is, that being with someone you love but can't bring you what you need from a relationship, you might want to break up to be yourself instead, even if you end up being alone... And I guess I would do the same if I was with someone who requested me to be mono, even without anyone else in mind, even if I ended up single, I'd rather be single and poly.