I am a veterinarian and as you can imagine we get some very emotionally charged cases. I have noticed that the newer the employee, the greater the likelihood of them crying during emotional cases such a euthanasia or critical emergency. In a few cases, my assistant was crying harder than the client. Over time, emotional control becomes second nature. You don't stop feeling, but you also don't lose it during a face to face with the client. (That comes later!) I think it's a skill that develops over time. Some in the human medical field call it professional detachment, but that's not entirely correct. You still have the emotions, but you learn when and how it is appropriate to express them. It also helps to have someone you can vent to outside of the emotionally charged situation.