What are childhood, youth, middle age and old age?

Childhood is a leaf that falls to the ground. I want to pick it up one by one, but it is also incomplete. Teenagers are cheerful laughter and long reading sounds. It feels like yesterday. Looking back, he is a young man drifting away. It is infinite passion, accompanied by ignorance and confusion. This is the midday sun, with a bright surface and a vibrant old age. I know something and let go to satisfy something.