by Percy Bysshe Shelley

We are the clouds that veil the midnight moon;      How restlessly they speed, and gleam, and quiver, Streaking the darkness radiantly!--yet soon      Night closes round, and they are lost forever: Or like forgotten lyres, whose dissonant strings      Give various response to each varying blast, To whose frail frame no second motion brings      One mood or modulation like the last. We rest.--A dream has power to poison sleep;      We rise.--One wandering thought pollutes the day; We feel, conceive or reason, laugh or weep;      Embrace fond foe, or cast our cares away: It is the same!--For, be it joy or sorrow,      The path of its departure still is free: Man's yesterday may ne'er be like his morrow;      Nought may endure but Mutability.