The heart, one of the most vital organs of the body. It is the center of the circulatory system and its main function is to pump blood to every inch of the body. Without the heart, one could not live. And for a man who has two hearts, living without one is simply painful. Although, it is anything but simple.
There is a man who used to have two hearts, but now he only lives with one. Why? Because long ago, he gave the other one to a pink and yellow girl. Now he survives, but barely. His pain runs so deep that he can hardly bear it sometimes. He puts on a happy-go-lucky front for his friends to see so they won't worry about him, but whenever he is alone, his thoughts turn dark and he thinks of her again. He thinks of a Rose that he will never see again, no matter how much he wants to.
This is set before Rose came back to the Doctor, just so you know.
As for the girl, she misses the man desperately, for she was stolen from him. Who stole her? The universe. Not our universe, but one very much like it. She was taken not by choice and now she has cried every night since, longing for her Doctor. Her heart she left behind with the man and until she gets back to him, she will never breathe easily again. But she had only one heart! How can she live at all now that she has none? She is living only on hope. Hope that one day, she will be able to get back to him.
One would say that these two people are heartbroken, but how can that be? Hearts cannot be broken. Do not think that I am being heartless myself, but truly I am correct. Hearts cannot be broken, for that is not how they are built. The Heart is a muscle, made out if tissue. To say that it can break would be to imply that it was made out of glass or another hard, yet fragile material. Hearts may not be broken, but they most certainly can be ripped. They are not easy to be ripped apart; it takes time. But that time they spent together, the time that caused their hearts to be ripped to shreds, they wouldn't trade for the world.