Coworker turned in 2 weeks, feeling devastated

I’ve realized over the last year in therapy that the reason I (mid 20s f) never made the leap to trying to make closer friendships is because in 6th grade, the one close friend I had killed herself. I never properly grieved over her death, and in my friend groups at school, I always had this feeling that they were all going to leave me one day, so I kept my distance and ended up being a ‘loner’ type.

Fast forward to now, and at my current job, there’s a coworker who I vibed really well with, and we’ve actually become good friends. They’re the only one I’ve shared my struggles with, and likewise, they’ve shared their difficulty managing their mental health issues. For a few years now we’ve hung out after work and on weekends, which has given me a lot of confidence in myself to help manage my isolation trauma…

…But now, my coworker is leaving for another job that offers better work from home and in office balance. They’ve talked about looking for another job for a while, so it’s not like this is out of the blue, but, I can’t help but feel we’re not going to be friends anymore. I’m going to go back to isolating myself.

A lot of people on reddit say that when they get a new job, they don’t keep up with previous coworkers, even if they were closer. My coworker has said we’ll still be friends, but my brain won’t stop spiraling to the worst case scenario for me.

I don’t have a therapy appointment for a few weeks, so I have to sit and wallow in this sadness and fear until then…