My heart aches, and a drowsy numbness pains My sense, as though of hemlock I had drunk, Or emptied some dull opiate to the drains One minute past, and Lethe-wards had sunk: 'Tis not through envy of thy happy lot, But being too happy in thine happiness That thou, light-winged Dryad of the trees, In some melodious plot Of beechen green, and shadows numberless, Singest of summer in full-throated ease.

-Keats,John
  Lamia, Isabella, The Eve of St.  Agnes and Other Poems,'Ode to a Nightingale', stanza1.