I think it hurts so much because there isn't an amiable parting of ways. pwBPD can't seem to say, "You're a good person, the fit between us just wasn't there". A very experienced psychologist that I talked to about this said that being able to recognize that the "fit" wasn't good and move on is a sign that one is ready for a serious relationship. pwBPD end things in a chaotic, blaming, immature manner. My pwBPD said to me, "You're the one who destroyed our marriage", as if it were as simple as that.
As far as our personal inventory goes, if we can say that the pwBPD is a good person (albeit very ill) and the "fit" simply wasn't there I think it bodes well for our future relationships.
As far as our personal inventory goes, I don't think we can say whether or not our BPD person was a good perso or not and whether or not it was truly a 'not fitting' problem. I agree that in all my previous r/s I could genuinly say the fitting wasnt great however between us nons and BPDers most will say the fit was great (and only in hindsight) it wasnt lesving the question, was it a good fit or not?
