“Once Later” by W.S. Merwin

It is not until later
that you have to be young

it is one of the things
you meant to do later

but by then there is
someone else living there

with the shades rolled down
how could you have been young there

at that time
with all that was expected

then what happened to
the expectations

there is no sign of them there
a shadow passes across the window shade

what do they know in there
whoever they are