"You Can't Have It All"

That's the title of a poem, by Barbara Ras, the entirety of which can be read here.  Here's a snippet that I particularly like:

"...[W]hen adulthood fails you,
you can still summon the memory of the black swan on the
pond
of your childhood, the rye bread with peanut butter and
bananas
your grandmother gave you while the rest of the family slept.
There is the voice you can still summon at will, like your
mother’s,
it will always whisper, you can’t have it all,
but there is this."

The obvious reading is to be grateful for what we have, because life is impermanent and fleeting. Yet somehow, the poem doesn't lecture us about it. In a way, it simply speaks to perhaps the most basic condition of our existence. You can't have forever, but you can have this moment.