I am falling out of love with this person who continuously splits on me and then doubles down for days before he finally comes to his rational thinking and apologizes and promises to work on managing the splitting.
I can sympathise totally. It's the gradual erosion and repetition that wears us down. Each time we hope 'this is the last time they'll do it'.. then it happens again and you have the image of being caught on the mouse wheel, never getting anywhere new and just going in circles.
In my own case, she wouldn't admit she had any problems, it was always 'someone else's fault' and she never apologised for anything she did. She knew I'd always chase after her even though I was the innocent one, which I now know just encouraged her to keep doing it. I should have set clear boundaries once I knew she'd keep doing it again and again.
Eventually she had one mega-split which made me realise that I either ended things or put up with her behaviour for the rest of my life. I chose to end it but, knowing what I now know about BPD, if I could go back I think I'd have tried for a bit longer, even though I'm sure the end would have been the same eventually.