"Never give all the heart, for love Will hardly seem worth thinking of To passionate women if it seem Certain, and they never dream That it fades out from kiss to kiss; For everything that's lovely is But a brief, dreamy, kind delight. O Never give the heart outright, For they, for all smooth lips can say, Have given their hearts up to the play. And who could play it well enough If deaf and dumb and blind with love? He that made this knows all the cost, For he gave all his heart and lost."

Source: William Butler Yeats (2000). “The Collected Poems of W. B. Yeats”, p.63, Wordsworth Editions