The Old Age of Nostalgia  by Mark Strand

Those hours given over to basking in the glow of an imagined
future, of being carried away in streams of promise by a love or
a passion so strong that one felt altered forever and convinced
that even the smallest particle of the surrounding world was
charged with purpose of impossible grandeur;

Ah, yes, and one would look up into the trees and be thrilled by the wind-
loosened river of pale, gold foliage cascading down and by the
high, melodious singing of countless birds; those moments, so
many and so long ago, still come back, but briefly, like fireflies
in the perfumed heat of summer night.

“The Old Age of Nostalgia” by Mark Strand, from Almost Invisible.