You are the element that is preserving humanity. If that element loses its defining properties, how can they ever be restored? The element is rendered useless, no better than a common rock used to pave a path.
You are the light of the world. You can see a city on a hill from a long way off at night time. Tell me, would you walk on a dark path with a flashlight that’s not turned on? No. You would turn on the flashlight so everyone can see where they are going. That’s you—the flashlight. Shine light on the path that leads to God. People will be grateful for the light, but only because it shows them the way.