On one hand, Earth and its atmosphere are finely balanced ecologically. There is just enough oxygen; water is recycled; the weather distributes warm and cool air and water. It seems as though the planet is a delicately tuned instrument—even fragile.
On the other hand, Earth has existed for over 4 billion years. Floods, volcanoes, mass animal extinctions come and go, and have an importance in maintaining the planet. Asteroids have slammed into Earth. Disease has wiped out whole populations. But Earth still exists.
Our perspective is skewed by the relatively minute amount of time we humans live. Our innate nature causes us care for Earth: the life on it; the substances of it; and the processes and events that occur as a result of it. This is our incredible Earth.