This is what I did: 1. I got a new hobby involving regular workouts and which was somewhat social with new people. Never really did sports before that, but this really helped me from getting isolated from society. I found new friends and got in shape. There is many of those, kayaking, rowing, soccer, ultimate, ... pick any one. Even running groups could work. Many evenings I came home tired after training, sometimes crying from heartburn, but that eventually passed. And 2. I finished the phd and then got a job in a different country, awesome place, new surroundings, own apartment, new colleagues, new life. This is rather easy with a phd. I didn't really click with my field either, but the decision to power through the last 1-2 years and just wrap it up and then move on was gold. That's what a phd signifies to a new employerand also yourself: You can finish something and power through, even if in tough moments. Every phd has those. Finally, after moving and new job and gotten in shape, got friends and a new relationship and it's great. I didn't have to fight for the latter, it just came autotomatically with new self confidence and casting a wide net. (I'm not really the social type.)
So, let your future self in 15 years tell you: this will all pass, you have a great future ahead!
P.S.: I also read self-help stuff and relationship advice and psychology. The moment I stopped, I started to feel so much better. It just reminded me how crappy I felt. Constantly. Once I threw this out I could embrace my new hobby and new beginnings. There will be throwbacks and evenings where you don't do anything but cry and eat chips. That's ok. Just don't let it consume you and steadily move on.