The trouble with pleasure is, the timing

One of the Butterflies

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 that 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 to pain.

— W. S. Merwin from The Shadow of Sirius