The Poetry Foundation website has this poem by Albert Edward Guest
entitled ‘It Couldn’t Be Done’.
Somebody said it couldn’t be done but he
with a chuckle replied
That “maybe it couldn’t,” but he would be
one who wouldn’t say so till he’d tried.
So he buckled right in with the trace of a
grin
on his face, if he worried he hid it.
He
started to sing as he tackled the thing
that
couldn’t be done, and he did it!