How do I cope with a job where mistakes can't be undone?

The thing pressing on you is that here a mistake does not get a second draft. It stays done. Living with that every day is genuinely hard, and it is normal that it weighs on you. That awareness is not a problem to fix. It is part of what makes you safe to have on the job. But awareness can turn into a constant low fear that wears you thin, and that helps no one. The way through is not to care less. It is to pour that care into the parts you control: your preparation, your attention, your discipline in the moment. When you have truly done your part with care, you have met your responsibility. You cannot also carry every outcome the universe might produce. Try ending each shift by asking one question: did I do my part with full care today? If the answer is yes, let yourself set it down for the night. The stakes are real and they always will be. You handle them by being disciplined and present, not by being afraid every waking hour.