“One of the Butterflies” by W.S. Merwin

The trouble with pleasure is the timing
it can overtake me without warning
and be gone before I know it is here
it can stand facing me unrecognized
while I am remembering somewhere else
in another age or someone not seen
for years and never to be seen again
in this world and it seems I cherish
only now a joy I was not aware of
when it was here although it remains
out of reach and will not be caught or named
or called back and if I could make it stay
as I want to it would turn into pain