In a PhD dissertation of someone by the name of Andrea Medaris, whose title is "The State of Being in Love" (who said PhD dissertations had to be boring?), I found an especially poignant and thought-provoking piece. I think it's worth reading slowly:
"The definition of passionate love describes a state where something is missing, and desperately wanted. That state is called love, as if the person has already obtained that which is desired by the mere fact of wanting it. Many people crave that state of wanting after the desire has been satisfied and they have their love object, wishing often to return to a time when they were not sated. Passionate love is viewed as more pure and exciting than the companionate love that may be felt later in a relationship. Perhaps because of this cultural value, passionate love has taken on an almost mythic tone, and longing for one’s partner seems to be an ideal state. Many human beings seem to want to want, and so they continue to seek passionate love via their existing relationships, or they end them and search again, finding repeated experiences of novelty that momentarily provide them with that intense longing."