It wasn't as if the Doctor thought through the reaction. One moment, she was nibbling on his neck.
The next, he flipped them on the bed, and his lips hovered a mere breath away from his. Really, there was something to be said for reflexes.
"Rose, I..." he tried, but his throat couldn't quite form the words as articulately as he would have liked. The Doctor could see the timelines; two of them, clear as day. He could warn her that it had been a very long time, and that he didn't want to hurt or rush her, and all the same bollocks he'd been feeding himself to keep this from happening before Regeneration.
Or he could could kiss her, and let come what may.
His lips crashed against hers, hands moving to her hair as he pinned her against the bed. If she protested, he could still hold back. But for the moment, he wanted to let go.