How do you cope with a break up?

I was with a girl for six months long distance, we met, she was my first kiss. The date didn't go like she wanted to she put walls up between us and broke up but said we can still be together in the future, but I can't handle the changes between us and started getting anxious and so today I asked her if she still even loves me a lil bit like she used to and she said she can't so we said goodbye after we both blew up at each other. She called me selfish and a bunch of other stuff and a piece of work.

Idk what to do...how to cope with this. I really believed in my heart she was the one and was so comfortable with her in my life and not worried she'd leave me and now she told me I took her for granted. So am I always supposed to be worried and afraid the next girl will leave me? I think I'll be single for a while after this honestly, the girl has seen every single part of me inside and out, I kinda wish I hadn't exposed so much of me now.