There's a crystallization that goes on in a poem which the young man can bring off, but which the middle-aged man can't.

Go West, young man.

Go west, young man.

It is the fear of middle-age in the young, of old-age in the middle-aged, which is the prime cause of infidelity, that infallible rejuvenator

We know that the negative sentiments are more prevalent among the middle-aged rather than the young,

A young man is a theory, an old man is a fact.