Hands Made to Hold
And it's just so fitting, in a way.
All of his 900 years of life and he's never once been able to hold onto anyone or anything that really mattered. So many companions, friends, and loved ones all lost to the ravenous hunger of time itself.
There's something almost poetic about the tragedy of this moment: watching her kiss someone who looks like him but isn't and knowing that this is what ought to be, this is how the universe has decided to give him what he wants for once. Of course it'd be given to him in a way that makes him sick, makes him want to break all the rules of time and space just to erase these images from his mind.
Everything he touches turns sour. They're holding hands and he can almost feel it himself, like an echo resonating back to him across a long distance. His hands were made to fit hers, made to hold them tight and never let go.
Why did he ever let go?
She's slipped right through his fingers. He'd thought it had hurt that first time, here at Bad Wolf Bay, but it's nothing compared to what he feels now. He had almost accepted it, had almost made peace with the fact that she was gone and wasn't coming back. And then she'd walked right back into his life, all blonde hair and tongue-in-cheek-smiles and Rose. And for a short while, he'd deluded himself that he could keep her, that they could finally be together.
He should have known that it would never work out like that.
He supposed it was a slight comfort to know that in one universe, one permutation of time and space, he got to keep her. He'd told her that in all the dimensions and universes that made up existence, there was only one Doctor. It had been true when he'd said it, but now there are two Doctors and the one that gets the girl is one that least deserves it, the one who just murdered an entire species (again!).
This whole body is for her. Every cell, every hair follicle is imprinted with her essence, with the essence of a kiss and Bad Wolf and the Time Vortex all mish-mashed into one being. Yes, this entire body was formed specifically for her, but the hands in particular. He'll never feel whole without her hands clasped in his own, and his doppelganger must feel the same way as well. He was grown from a hand, for goodness sake—he was never meant to do anything but hold onto her.
And therein lies the beauty of it, he supposes. That he could embrace Rose Tyler and lose her in all the same moment.