"It's me, Rose," the Doctor repeated gently. "I'm him."
Perhaps he should have gone about this a different way. Perhaps he should have prepared more. Though, what could he have done? Changed back into the leather jacket and jumper and dark pants and boots he'd worn as his ninth self? Why? It wouldn't have proven anything except his ability to find the wardrobe and get dressed. Prepared a video record of events inside the TARDIS so he could show Rose what had happened? That would have been even more cruel than having to tell her that he was going to change, in her future. That he had already changed, in his past. No. It was far better to come at the problem head-on, as he'd done before and was doing now. She deserved the truth.
"I know this is difficult. I know you wanted me to be ... well, him. The other me. The same Doctor you first met, with the daft big ears and Northern accent and short hair and the U-boat captain look. I'm sorry, Rose, but I'm not him. Not anymore. And I can't change back."