When I looked up from my blank page
there was an angel in the room.
A rather common place angel,
presumably of lower rank.
You cannot imagine, he said,
the degree to which you're dispensable.
Of the fifteen thousand hues of blue,
he said, each one makes more of a difference
Than anything you may do
or refrain from doing,
Not to mention the feldspar
or the Great Magellanic Cloud.
Even the most common Plantain, unassuming
as it is, would leave a gap. Not you.
I could tell from his bright eyes -
he hoped for an argument, for a long fight.
I did not move.I waited in silence
until he had gone away.

Hans Magnus Enzensberger

http://www.poemhunter.com/poem/the-visit-25/