In juniour high school we studied a poem that began with reflection on youth (ie: 'When we were young...'), and ended with the idea that since the writer is older, the 'key to the kingdom' is lost (imagination/vitality?) and 'age is the graveyard' of hopes and dreams. The text contains references to sailing with Columbus, playing Cowboys and Indians, diving with Captain Nemo and other child-oriented games and devices (cardboard box vessels!).
I don't know who wrote it or the title. Can someone help me please?