How do I leave? Leaving at the top of the cycle seems cruel, leaving at the bottom feels impossible.

I know, deep down, that this cycling will kill me eventually, but I feel powerless to get out.

I'm lucky (??!?!?!) that we have so much time in 'Honeymoon' phases but the love bombing has just begun to feel false, or sincere but so unhealthy. It's like the arrow on the FedEx logo: once you see it you can't NOT see it.

At the bottom... I know, emotionally, they're just a child. Their parents are NPD/BPD or whatever weird amalgamation of it they've created over their lives -- I refuse to cultivate any sort of closeness to them -- and they left my pwBPD emotionally crippled. How can I leave when I know behind the tantrum there will be despair and emptiness? It feels even like the ultimately callousness.

It seems like the only way out is to shut off location on my phone, block them, find a place to crash other than my own apartment for a while... but how do I accept that this is really the best course, for both of us, since I know I don't trigger them -- I am a trigger? DBT has helped them a little but I feel like it's just given them more tools to control others with, not themselves.

I'm not sure what I'm looking for, advice wise. I feel like I know what to do, I just can't make myself hard and cold enough to actually pull the trigger, and I've been trying. How do I become so cold? How can I do what's best? How can I accept that mercy will, from the right angle, appear like cruelty to even myself?