I do identify. I have found a couple of things helpful: one, trauma recovery therapy, which is healing and gets my various fragments working in my own best interests almost involuntarily. (I do lifespan integration,
www.lifespanintegration.org.)
Two: just resolving to do one constructive or hard thing each day even when I don't feel motivated -- make the goal reasonable, but when you get there it's strengthening and eventually you can do more and more.
Three: if possible, assess who else who is actually good to you needs you to not fall apart, and commit to come through for them. Parents? Good friend? Sibling? In my case this is my kid.
I have spent a ton of time where you are, and fell apart/came very close to falling completely apart after each episode with my ex ended badly. For a long time I functioned at 10-20% of my formerly vibrant and productive self. Amazing the impact of this on our confidence and appetite for living. At this point, anyone looking in would see a happy and productive person again. That is far from the whole story--I still feel emotionally numbed out--but I think that may thaw once I have a viable life humming along again.
My heart goes out to you Infern0. You've tried so sincerely. Your BPD person like mine seems to get a lot out of escaping true intimacy. Not much we can do about that.