The Doctor smiled. It was a small, rueful smile, but a smile nonetheless.

He won't love you.

If he isn't you, I don't want him to.

He remembered the terror that John felt, and how he knew the Doctor wouldn't love Joan, and how he knew the Doctor couldn't love Joan, and so he didn't want to lose that.

"You're afraid," he said, "That you're going to die. This you that you've discovered. I understand."

Another move of intimacy, this one to bring her into a hug.