A poem about "movement toward the barely possible"

Here's one of my favorite poems. I think it creates some nice images that mesh with the whole idea of running long distances and pushing yourself to your limits. Isn't it all about, as the poem says, movement toward the barely possible.

Letting the Puma Go by Stephen Dunn

I'll make a perfect body, said God,
and invent ways to make it fail.
- lines removed from the poem

He liked to watch the big cats.
He liked their beautiful contempt,
yet imagined how they might change
and love him
and stretch out near his feet
if he were to let them go.
And of course he wanted to let them go,
grateful for the iron bars, the lock.
He'd heard the tiger succeeds
only once in twenty hunts -
the fragile are that attuned
and that fast -
and was confused again about God,
the god who presided here.
He'd watch the tigers at feeding time,
then turn to the black panther,
its languid fierce pacing, and know
it was possible not to care
if the handsome got everything.
Except for the lions.
Hadn't the lions over the years
become their names, like the famous?
But he could spend half an afternoon
with those outfielders,
the pumas, cheetahs, leopards.
So this is excellence, he imagined:
movement toward the barely possible,
the puma's dream
of running down a hummingbird
on a grassy plain.
And then he'd let the puma go;
just before closing time
he'd wish-open its cage
and follow it into the suddenly
uncalm streets,
telling all the children it was his.