How do I keep my job from hardening me?

You are trying to do a hard thing well: stay firm enough to keep control and humane enough to stay yourself. The fact that you notice the environment hardening you, and that you do not like it, is exactly what will save you. The ones who lose themselves are the ones who stop noticing. Hardening is contagious in a place like yours. It seeps in because it feels like armor, and some of it you truly need to do the job. The danger is when the armor stops coming off at the end of the shift and starts to become who you are, at home, with people who never earned that edge. So build a border between the work and the rest of you. Find one small ritual that marks the end of a shift, and one relationship or place where you practice being soft on purpose. Notice when you are carrying the hardness where it does not belong, and set it down. Staying human in that environment is not automatic. It is a discipline, and you are already practicing it by paying attention.