I think youth refers not only to the physical state, but also to the psychological state.

In poetic terms, being young means that you still regard the world as picturesque; Young, the world sees you as pure as tea.

Age should only be a part of measuring youth, not the whole. The heart is not old, but always young. How many people are still young in their sixties and seventies? They are still fighting for their dreams. Don't let the culture of the times become the sorrow of the times. At any time, the culture of a society should be positive, not just younger than anyone else.