It's common for people to identify with their job too much, independent of employer. It almost feels like it's a rite of passage to pour everything into your first job in your early to mid twenties, especially if you're a high performer with something to prove and you're lucky enough to work on something that "really matters". What I've seen is most people go through a period of mild depression / burnout, realize that a job can be a fun and rewarding part of life but isn't life in it's entirely, and then live on more happily after learning to keep some distance.