The definition of Self-fulfilling Prophecy
ideas that become reality simply because someone believes them
this definition fits a person with BPD because they can only see the idea of what can be in a relationship hence the repeating pattern.
the honeymoon stage you talk about is the ideal they have in their heads and when that ideal is realized to be imperfect (because as human beings it is normal for us as non BPD's to show our imperfections to the ones we love and trust never thinking they will be used against us) they find it hard to accept and that is when the honeymoon stage is lost.
When my ex partner realized my imperfections he needed to seek out the ideal... . in his mind to start over in hopes of getting it right even though he was still with me no matter how many times it takes... . he needed to lash out at me because I destroyed his ideal of the perfect relationship... . what he needed to not feel empty. It wouldn't have mattered how perfect we tried to make it to keep it in that honeymoon phase he could not change that fact he was always empty and sad
I don't think you were meant to meet her... . to endure... . to lose yourself only to have to repair the damage caused by being in the relationship. You met her and you chose to be with her for reasons only you can understand but I don't believe it was "fate" or your "destiny"... . no one deserves that. (just speaking from the heart)