He wanted to get to know River. His own nagging curiosity would always get the best of him. He had come so close to being able to peek inside that book of hers, though ultimately let it be at the library. It would be found and archived, then likely never touched for the rest of time except by pure chance. That suited him fine, he'd discover his future the proper way. The long way.
With another face.
"I'll make good on that," he said honestly. "No doubt."
The only thing that could complicate matters worse would be if his wife on Gallifrey ever turned up. If that ever happened, the Doctor knew exactly what he would do: get in the TARDIS and disappear. Perception filters would keep him out of sight, utter radio silence would give him the chance to sort out his thoughts. But, he didn't think it possible. Or maybe he only hoped for it because the Doctor was so attached to his present.
He did manage a bit of a grin at her prodding. "I think you're right. She called me pretty boy though, Rose. Pretty. Still haven't decided how I feel about that."
Abruptly rolling onto his back, the Doctor kept close enough to her so that he could keep a grip on her hand. He always needed that, it was one of the important things to get through any facet of the universe, after all. The trouble with River for the Doctor was the caliber of her specialness. Much like Clara, he was ill-prepared for what their existences entailed.
Everything he knew was turned upside down. He could only imagine how the previous him would feel about it all, too.
"She thanked me, River," he said after a prolonged pause on his part. "For saving her. Literally saving her and uploading her consciousness into a computer. In the back of my mind, I'd wondered if that was the right thing to do. Suppose it was."