The Doctor loved Rose, more than he’d ever loved one of his human companions. She was so young, vibrantly alive, enthusiastic about meeting the universe head-on, but he’d known from the start it couldn’t last. He could never be what she needed.
When she’d been pulled into Pete’s World he’d thought that was it, but she’d found a way across the void between universes, returning to his side. Now he was sending her back.
He knew she’d see it as rejection, but he was setting her free with his other self, the only part of himself he could give her.