That moment. That moment when he laid eyes on her again, after so long.
He hadn't allowed himself to even think about Rose too much after she was taken from him. In a way, it was a blessing that Donna appeared in the TARDIS when she did, as it meant he wouldn't have to go through grieving for his friend. His companion. His soulmate.
And it had been so long. When he turned around, not even daring to hope that he was going to see what he desperately wanted to see, he saw a different women in front of him. It was still her though. The blonde hair, that beautiful big smile. But her youthful innocence that she had when she first stepped into the TARDIS all that time ago had gone. She'd seen wars, death and destruction since then. But for that moment, all those thoughts were pushed from the Doctor's mind as he thought only one word.
Rose.
His Rose. His wonderful, beautiful, clever Rose.
The Doctor had never run so fast in his life. He didn't take his eyes off her. An almost fatal mistake and as he lay on the ground, for one terrifying moment he thought it had all been a dream, and she wasn't really there. But then her face appeared over him, and she held him. It was a homecoming.
Later, the Doctor would tell Rose that he had never wanted anything more in his life than to not regenerate again. He needed to see Rose with this face and love her with these hearts. He remembered the look of fear in her eyes when she thought she was going to lose him again, after all this time.
And then there she was, standing in front of him, her big eyes looking up at him. Rose. Beautiful Rose. She threw her arms around his neck and in a second, he had her back. And in that second he felt all the grief, all the sadness melt away as his soulmate was back.
His Rose.