Because he is a being who can see timelines, he knows exactly what he's missing. Sometimes he goes to a quiet, pastoral planet and lies out under the sky, picturing how they are. It makes him smile.
A wistful smile, but his feelings of warmth aren't lessened, for all that they're vicarious. He plays with percentages in his head, imagining their adventures. He is quite glad that he cannot visit.
He knows that Rose Tyler, his fantastic girl, will gather joy unto herself. He rather likes that image. He can see her, face glowing, finger painting joy across his skin.