My favorite quote in The Symposium comes from Aristophanes, who gives a mythological account of human origin to explain the innate longing that humans have for love. He concludes: " 'love' is the name for the desire and pursuit of wholeness."
To give you a bit of background, here's Aristophanes' myth animated for your viewing pleasure. Admittedly it's a bit different than the version I pictured in my head, and you have to read the subtitles unless you speak French, but it's thoroughly entertaining nonetheless...