This is one stanza from a long poem , “Limitations” by the British poet Siegfried Sassoon:
I told you it was easy! …
Words are fools …Who follow blindly, once they get a lead.
But thoughts are kingfishers that haunt the pools
Of quiet; seldom-seen: and all you need
Is just that flash of joy above your dream.
So, when those forty platitudes are done,
You’ll hear a bird-note calling from the stream
That wandered through your childhood; and the sun
Will strike the old flaming wonder from the waters…
. And there’ll be forty lines not yet begun.