For me personally, I've separated these 2 things to work on them separately. Because it's really miserable being isolated - I absolutely hear that and relate to it a lot.I am down to only one person in my life because my inability to feel any sort of safety leads me to destroy everything.
So, for me, it's now 2 separate issues:
1) I always fee unsafe (that's gonna take a long time to shift - feelings tend to do their own thing);
2) I destroy relationships.
That number 2 is a behaviour. I'm doing it because of (1), but behaviours, unlike feelings, I can definitely change. Yeah, practice. But if I work on it, I can change the way I behave, even though I'm still feeling unsafe.
So, I'm starting to create healthy relationships, even though I feel unsafe. And that's helping a lot with the isolation.