How do I deal with anxiety about one thing breaking and ruining everything?

You see how connected it all is, and that is exactly why the fragility frightens you. One weak link can pull the whole chain. Knowing that keeps you alert, but held too tightly, it turns every quiet moment into waiting for the next break. Here is the truth you already sense: you cannot make the system unbreakable. Things will fail. What you can build is the ability to catch a failure early and respond well. A chain that never breaks is a fantasy; a chain you can repair quickly is real strength. So move some of your worry into preparation. Pick the one link whose failure would hurt most, and give it a backup or a plan. When you know what you would do if it broke, the fear of it breaking loosens its grip. You trade dread for readiness.