Henry Wadsworth Longfellow

Ohthat a Song would sing itself to me
  Out of the heart of Nature, or the heart
  Of man, the child of Nature, not of Art,
  Fresh as the morning, salt as the salt sea,
With just enough of bitterness to be
  A medicine to this sluggish mood, and start
  The life-blood in my veins, and so impart
  Healing and help in this dull lethargy!
Alas! not always doth the breath of song
  Breathe on us.  It is like the wind that bloweth
  At its own will, not ours, nor tarries long;
We hear the sound thereof, but no man knoweth
  From whence it comes, so sudden and swift and strong,
  Nor whither in its wayward course it goeth.