How do I handle a job where a mistake could kill someone?

You live with a truth most people never have to face at work: get it wrong, and something burns or someone dies. That is a heavy thing to carry to bed, and the fact that it keeps you up shows you understand exactly what is at stake. That understanding is not a curse. It is the very thing that makes you careful enough to be trusted. But fear and care are not the same, and only one of them helps. Care does the calculation right, checks it, follows the code, and then trusts the work. Fear does all that and still lies awake, as if worry after the fact could reach back and change what was already done correctly. It cannot. It only robs you of the rest that keeps your hands steady tomorrow. So put your faith in the method, not the dread. You keep people safe by doing the work right, every time, not by worrying about it every night. When the fear comes at 2 a.m., ask: did I do this one properly? If yes, that is where safety lives, and you have already done your part. Let the good work be enough to sleep on.