How do I handle a job where one mistake could be catastrophic?

You have real autonomy and real reward, and underneath both sits a pressure most people never feel: one lapse could cost everything, so you can never fully be off. That is a heavy way to live. The isolation is not in your head. Few around you understand what it is like to hold that line with no margin. The vigilance that keeps you sharp is also what wears you thin, so the goal is not to care less — it is to give the pressure somewhere to go besides your own chest. Trust your training and your systems. The checklists, the double-checks, the routines exist so that being safe does not depend on you being superhuman every second. Lean on them, and let them carry part of the weight. And break the isolation on purpose. Find even one person who does this work and can hear the truth of it without you having to explain. When you are off, practice being actually off — a hobby, a walk, something with no stakes at all — so your mind learns there is life outside the razor's edge. You can be excellent at this and still be a person. Protect the person.