Plenty of good suggestions here, I don't have another one to add, let alone a better one. But I'll tell you this: you are not alone, this happens (a lot) and odds are it is not your fault. You asked how to deal with it, a lot of the stuff other comments said boils down to realising your professional universe is not so $negative_characterization_here like the place you are currently living in, it just seems that way probably because like a boiling frog you tried to adapt without seeing the hit coming, and came to think that's "normal" and you can't take "it" anymore. Time for a change, you'll do great in your next corner of the universe, and even if you find yourself into another bad one you'll recognise it soon enough and either fix it or leave it.