Then he let you drive. His TARDIS! I know! He let you put your hands on that old blue angel, and you steered her for awhile. Just long enough for a call from the Doctor's daughter. Well, one of them. Mad Martha, soldier Martha: calling the Doctor back to Earth, presenting her accomplishments and her fiancé like a child with a trophy. She was engaged, too. And she was a soldier -- oh, he didn't like that! The Doctor hates armies, unless they are his own. He was born in war and fire and destruction, twice in succession with more to come: he hates the war because it rides in fire along his blood. His two hearts beat against it.
But that's fine for divinity, isn't it? To disappear, when mortal pain intrudes? It's left to us, to the children of time, to carry on in his wake. And that means battle, strategy, time's arrow moving forward in a single direction, choices with consequences... All the things a lonely God doesn't really understand. Things Martha learned in his absence, and puts to use even now. He can afford to get bitchy about it, because -- like all children do -- she's covering his ass. Like Harriet, like Rose, like Astrid. There are things he will never understand, because he is a God. He sees the world turning, the fixed points in time, the potential for darkness and for greatness, but he doesn't know the slow path. How hard it is to save the world with just your hands and sweat.
This is what it is to be a soldier: to be the one to do the things that other people must not do. In this case, in the case of the children of time, to do the things the Doctor can't do. Not because he's better, or a hero, not because he's stronger or weaker, but because they are happening here, now, right in front of us. And here and now are never what's in front of him. He can never truly love, because love's desperation arises from the death of moments. It is sweet because it ends. And he never does. When he loves, it is half-hearted.
Rose/Eros never knew that -- the Doctor never knew that, with her -- which is why their story never really ended. Martha/Philia figured it out with a quickness, and it burned her strong. But you... There is no desperation in your love, because there is no passion in it. It is just love. It's just the library of love: Agape. It is what all love becomes.
That year on the Valiant, it wasn't the Doctor's fault. Martha knew that. But she also knew this: he burns. Like fire, and ice, and rage. He's like the night and the storm and the heart of the sun. Martha knew what he is always almost turning into: she knows the beating of the God's heart, in that tiny man's body. How it wants to burn with you. You went to visit your mother, and grandfather. He made the Doctor swear to keep you safe. I wonder if he regrets that now, somewhere alongside?