THERE are gains for all our losses,
There are balms for all our pain:
But when youth, the dream, departs,
It takes something from our hearts,
And it never comes again.

We are stronger, and are better,
Under manhood’s sterner reign:
Still we feel that something sweet
Followed youth, with flying feet,
And will never come again.

Something beautiful is vanished,
And we sigh for it in vain:
We behold it everywhere,
On the earth, and in the air,
But it never comes again.

Richard Henry Stoddard

http://www.poemhunter.com/poem/the-flight-of-youth-3/