The one which keeps coming back to my mind every now and then is this one by Robert Frost. He wrote in his "Stopping By Woods on a Snowy Evening" :
"The woods are lovely, dark and deep.
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep."
This is one piece of verse I have heard so many people use. I grew up listening to these quotes because they were very often recited by our school Principal, Nalini Miss and they had caught my fancy since then.
Another masterpiece would be from John Keats', "An Ode on a Grecian Urn" which goes like:
"Heard melodies are sweet, but those unheard
Are sweeter"
Then this one from William Shakespeare's Macbeth:
" All the perfumes of Arabia will not sweeten this little hand. "
Some quotes from William Shakespeare's Merchant of Venice:
"But love is blind, and lovers cannot see The pretty follies that themselves commit."
"All that glisters is not gold."
"The quality of mercy is not strain'd, It droppeth as the gentle rain from heaven Upon the place beneath. It is twice blest: It blesseth him that gives and him that takes."
"A goodly apple rotten at the heart: O, what a goodly outside falsehood hath!"
A quote from The Alchemist:
"When a person really desires something, all the universe conspires to help that person to realize his dream."
And this one last quote that I came across in a facebook application, which is supposed to be a heartbreak quote:
There are still so many quotes, so many of them that are simply too good, but I have promises to keep and miles to go before I sleep and......