OK - I'll give this a shot. Most of what I've thought about in conjunction with this "friend after romantic relationship" thing comes from observing Hol's tribulations in this. That may NOT however, apply to you. So maybe grist for the mill, while sorting out your own feelings about this? Mind you, this is all speculative - because many combinations of "relationship" at different levels can be possible between two people - depending on the people & circumstances. Of that, I'm certain. Does it happen? Not that often.
In Hol's age cohort the "friends with benefits" phenom is quite common, but they didn't invent it. I'm not sure we did either - but we were no stranger to it either.
I have watched her multiple times, try to maintain some kind of friend contact - with her ex-husband (went OK; but only a decade after they divorced); a couple of other relationships; then this last long-term one. The last one - let's call it the MB decade - she fought tooth & nail and was party to wearing her self-esteem down to get him to acknowledge that what she felt, thought, said and wanted was just as important in the relationship as his wishes. The last half of their time together was full of heated arguments & hurt feelings on a regular basis. It was exceedly tedious and painful to witness for me. Just make a decision already! LOLOL.
Then it dawned on me that it was a power struggle. That what she wanted was for him to participate, engage, with the situation between them... and she was determined to stick out the suffering even though her feelings for him were pretty much nil at that point; she was miserable - even tells the story to this day that she had to repeat to herself "I'm good at my job" on the drive to work because MB would discount how difficult her work was. This youngish woman has always had a healthy ego... and been extremly strong emotionally and in her self-value. She knows she's capable, competent, independent and effectively compassionate. But she was on the edge of losing that, especially the last year.
Her relief when he finally decided to break up was just as intense. She took the road trip, with Knuckles, to re-discover what it felt like to just be her again... and while the trip was longer than initially planned, she did accomplish what she set out to do. About 2 months. But then ensued the campaign to try to maintain friendship. Of course, there were loose ends to tie up on the business side of spending a decade with someone.
Over the course of 3 years, talking about this - it still comes up for her, intensely emotional at times - she's been able to say that she is trying to "win". To wheedle, cajole, reason, find just the right metaphor or analogy - to make him see that she wasn't a bad person just because she was DIFFERENT from him, and felt/thought things different than he did. She made gestures; left messages; even visited him to pick up/move stuff with the current BF - who was engaged with on a mutually respectful level, but not HER.
MB had even gone to far as to concoct a total fantasy of how evil she was to MB during the relationship and tried to shop that to her friends -- who'd been "in the loop" of her confidence all along. When confronted on it - he simply slunk away. But Hol wouldn't give up trying... hoping... that some day, some how he would "see the light" and there could be a full debriefing of what happened, apologies on both sides, shake hands and know the other wasn't seen as a villain.
That was the stakes in the power struggle. Ultimately, she did NOT win that time. But she fought and in some ways still struggles for a way to fight longer - because the reality of her, then & now - is not what he thinks or manufactured a fantasy of what it is. Somehow - her self-image is tied to succeeding in that struggle.
So that's how I understand fighting to maintain a friendship after a romantic relationship. It's foreign to me; especially how it's important to her to "win" in this struggle.
More later; gotta go.