How do I carry the weight of risks I can't see in my work?

You are starting to feel the moral weight of what your systems might do if they fail in ways you cannot see. That feeling is heavy, but it is also right. The engineers who feel nothing are the ones who build carelessly. What you are carrying is the seriousness the work truly deserves, and it means you are the kind of person it should be trusted to. But weight can either sharpen you or crush you, and you get some say in which. Carried well, it makes you thorough, humble, willing to double-check the thing you would rather assume is fine. Carried badly, it becomes dread that helps no one. The difference is turning the feeling into diligence instead of just fear. So give the weight somewhere to go. Let it push you to do one concrete thing, review the failure modes you have been avoiding, and address the worst one. You cannot see every hidden risk, and you are not required to be perfect. You are required to care enough to look hard, and then to build as well as care allows.