Our lives, discoloured with our present woes,
May still grow white and shine with happier hours.
So the pure limped stream, when foul with stains
Of rushing torrents and descending rains,
Works itself clear, and as it runs refines,
till by degrees the floating mirror shines;
Reflects each flower that on the border grows,
And a new heaven in it's fair bosom shows.

Joseph Addison

http://www.poemhunter.com/poem/hope-411/