A very tough question indeed & i have got two, but their not really quotes more of a suggestion....One's by Bruce Lee & it's on philosophy, & it's the best way to live our lives without suffering....Basically it's all the Buddha's teachings in a nut shell, & it goes like this:
"Be water my friend", which actually has a deep powerful meaning believe it or not, because i bet you was disappointed after the build up i gave it!lol
Another one i live my life by, & my mind has accepted as a fact so it's quite easy for me to do is the following:
It's by Alan Watts who was an English Philosopher, but who has since died.
"You do not want to get into the ridiculous situation, of being a dog wagged by it's tale", again another suggestion with a deep powerful meaning.