"He's not you."

The retort came abruptly out from her lips, sharp and almost caustic before Rose could stop herself or even think about doing so, and she was actually surprised at her own vehemence. It wasn't directed at the Doctor, of course, not in the slightest, but the truth was that what she said had been exactly what was bothering her. There was no replacing the Doctor, he was exactly what he was.

A streak of colour moved up her throat and cheeks, and Rose dropped her eyes. "Sorry, didn't mean to snap like that."