When you work closely with certain people, they get adopted as part of your Work Family. My previous employer, I worked with for 8ish years. I worked the same schedule as a couple of my coworkers for years. We got to be incredibly close.
So when I had a mental breakdown and left, that part that was so close with them suffered. Our usual thing was going to a restaurant and hanging out and chatting and whatever.
We've been chatting again. It's been about 5 years since I've seen them and it just...feels really nice.