"What do I think of love? - As a matter of fact, I think nothing at all of love. I'd be glad to know what it is, but being inside, I see it in existence, not in essence...  discourse though I may for years at a time, I cannot hope to seize the concept of it except "by the tail": by flashes, formulas, surprises of expression, scattered through the great stream of the Image repertoire; I am in love's wrong place, which is its dazzling place: "The darkest place, according to a Chinese proverb, in always underneath the lamp."
~ Roland Barthes, Lover's Discourse

"In real love you want the other person's good. In romantic love you want the other person" 
~ Margaret Anderson, founder and editor of The Little Review

"Love is composed of a single soul inhabiting two bodies" 
~ Aristotle

"Take away love, and our earth is a tomb"
~ Robert Browning 

 "Love is that condition in which the happiness of another person is essential to your own."
~ Robert A. Heinlein

 “Love is just a system for getting someone to call you darling after sex.”
~ Julian Barnes

 “yes, and how he kissed me under the Moorish wall and I thought well as well him as another and then I asked him with my eyes to ask again yes and then he asked me would I yes to say yes my mountain flower and first I put my arms around him yes and drew him down to me so he could feel my breasts all perfume yes and his heart was going like mad and yes I said yes I will Yes.
~ James Joyce, Ulysses, last words.

 “This is the monstrosity in love, lady - that the will is infinite and the execution confined: that the desire is boundless and the act a slave to limit.”
~ Shakespeare, Troilus and Cressida

 “I need to possess this woman in order to save myself from the absurdity of being in love with her.”
~ Pierre Laclos, Les Liaisons Dangereuses

 “I've been making a list of the things they don't teach you at school. They don't teach you how to love somebody. They don't teach you how to be famous. They don't teach you how to be rich or how to be poor. They don't teach you how to walk away from someone you don't love any longer. They don't teach you how to know what's going on in someone else's mind. They don't teach you what to say to someone who's dying. They don't teach you anything worth knowing.” 
~ Neil Gaiman, The Sandman, Vol. 9

 “Love is a temporary madness, it erupts like volcanoes and then subsides. And when it subsides, you have to make a decision. You have to work out whether your roots have so entwined together that it is inconceivable that you should ever part. Because this is what love is. Love is not breathlessness, it is not excitement, it is not the promulgation of promises of eternal passion, it is not the desire to mate every second minute of the day, it is not lying awake at night imagining that he is kissing every cranny of your body. No, don't blush, I am telling you some truths. That is just being "in love", which any fool can do. Love itself is what is left over when being in love has burned away, and this is both an art and a fortunate accident.”
~ Louis de Bernieres, Captian Corelli’s Mandolin

 “Everyone, at some point in their lives, wakes up in the middle of the night with the feeling that they are all alone in the world, and that nobody loves them now and that nobody will ever love them, and that they will never have a decent night's sleep again and will spend their lives wandering blearily around a loveless landscape, hoping desperately that their circumstances will improve, but suspecting, in their heart of hearts, that they will remain unloved forever. The best thing to do in these circumstances is to wake somebody else up, so that they can feel this way, too.” 
~ Lemony Snicket, Horseradish: Bitter Truths You Can’t Avoid.

 “Love never dies a natural death. It dies because we don't know how to replenish its source. It dies of blindness and errors and betrayals. It dies of illness and wounds; it dies of weariness, of witherings, of tarnishings.”  
~ Anais Nin

 “People think a soul mate is your perfect fit, and that's what everyone wants. But a true soul mate is a mirror, the person who shows you everything that is holding you back, the person who brings you to your own attention so you can change your life.... A true soul mate is probably the most important person you'll ever meet, because they tear down your walls and smack you awake. But to live with a soul mate forever? Nah. Too painful. Soul mates, they come into your life just to reveal another layer of yourself to you, and then leave."
~ Elizabeth Gilbert, Eat Pray Love

Thanks to Goodreads.com for the last 5 of these quotes....