How do I stop worrying about making a costly mistake at work?

You hold a business's whole financial picture, and the fear that one wrong number could cause real damage sits on you all the time. That fear comes from caring and from understanding the stakes. It is not foolish. But left unchecked, it becomes a weight that makes the work harder, not safer. The honest truth is that everyone who does careful work will eventually make a mistake. Perfection is not the goal, because it is not possible. What actually protects you is a good process: double-checks, reconciliations, backups, a clear trail. A strong system catches errors before they grow. It turns one fatal mistake into a small thing you caught and fixed. So put your energy where it helps. You cannot will yourself into never erring, but you can build the habits that make errors small and recoverable. One step: pick the one task where a mistake would hurt most, and add a simple second check to it this week. Trust the process you build, and let the fear settle into ordinary care.