Yahtzee said:
"I believe that what people call 'love' is a combination of herding instinct, peer pressure, need for security and good old-fashioned lust."
Throw addiction into that mix and you're right on the ball.
First the herding instinct/lust get people to be attracted to each other. Once the instinct part wears off (which it does) people have become so used to their partner's habits and them being a part of their lives that they start to feel like their lives will no longer be complete without one another.
After a breakup, people often show the same symptoms as a junkie or smoker trying to kick the habit. Some fine examples would be replacing the old addiction with a new one (the rebound) or staying clean for a while and then running back to the old drug. (getting back together or stalking)
Even if someone finds a new person to get addicted to, it will still be like using a different drug, they'll miss the old addiction until they've completely worked it out of their system.
Peer pressure and the need for security are rather redundant in this context, since the need for security most people have was created by the image implanted by their peers.
Theres no denying the peer pressure part either. Open any book, turn on the tv, play a game, listen to the radio and all you read, see and hear about is everyone and their dog finding 'true love'.
Also, before anyone claims this is just some random pessimistic theory written by a bitter and lonely man, and they've experienced true love, all of the above has been proven by actual scientists and psychologists doing thorough research.