The Doctor knew he couldn't. Oh, there would be times he could endure a few clips here and there. He had a particular fondness for glimpsing snippets of companions long since past, but never anything he hadn't seen with his own eyes. Nosy though he was, the Doctor didn't want to invade their privacy.
Just seeing something more than tangible than the memories sleeping in his head was enough to warm the nostalgia most days.
Attention solely on Rose then, the Doctor's mouth was a wavering flat line. It hadn't been so bad before. When he had regenerated to save her life, she had been there--bewildered and a little bit scared, but there nonetheless. He hadn't gone through it alone, not like he was doomed to do this time around. Before they'd dragged him into the TARDIS after the Dalek had shot him, just seeing her face had been enough for him to be content with moving on.
Then, of course, an opportunity had arisen for him to stay a little while longer.
First and last. In slightly better spirits than before, the Doctor dropped a kiss to her forehead, then tugged her close again. "I'm sorry, I have been caught up in it. Suppose I should be grateful that I've got extra regenerations as a backup now, more time to drag Gallifrey out from its pocket universe. Equally important, I've got you. Don't need the show, reality's far better, isn't it?"
Easing up in his embrace and disposition, the Doctor leaned back to genuinely smile at her. It wasn't perfect, but it wasn't meant to be either. He liked things this way, intricately imperfect. It kept him grounded, kept him believing that he could steal much, much more time with her while proudly wearing this face.