Disclaimer: I don't own Doctor Who and I'm not profiting from this.
Angst and rambling ahoy. Day 9 of my New Year's fic-a-day project (see my profile for fandoms and a schedule if curious).
It's a funny old thing, regeneration. Normally, when humans ask about it, he tells them that, after all, they become more than one person during their life, too. It's called growing up, and all well-adjusted species do it. The only difference is that the Time Lords do it a little more abruptly than most, and that their bodies change a little more drastically. And, generally speaking, he believes that. But…he doesn't want to go.
This body belongs to Rose. It was born in a blaze of love out of a sacrifice for her sake; she nursed it from newborn feebleness into health. These hands held hers, these eyes saw her, these ears heard her voice. This face and form were made to please her eye. Every cell of him will be altered, and every cell of him belonged to her, once. He doesn't want to change.
It's not just the face, either. This personality was created out of gratitude to the child who had healed his soul, to meet her needs as she had met his. Oh, he's always been a mad, thoughtless adventurer; some things even regeneration can't change. But each Doctor is a little different, and so many of the quirks of this one grow from things that Rose needed. This transparency is what Rose craved from her Doctor. Even his newfound ability to tolerate (not enjoy, but at least tolerate)parents and siblings and family dinners grew from the pain in Rose's eyes the time he told her that he didn't "do domestic." Even if these traits have laid him open to suffering, they bear Rose's fingerprints. He doesn't want to alter them.
Normally, when death comes knocking, he accepts that some change is coming, that whatever he becomes will balance the excesses of what he is. That's part of regeneration; the obliviousness of one phase is balanced by perception in the next, or a sharpness in one personality is replaced by sweetness in its successor. The chess master gives way to the romantic, though the soul beneath keeps its principles and values. This time, however, he knows what will be cut away, and he cannot bear to give it up. This body will never let go of Rose. Never. The replacement Doctor will let her slip into the sea of people he's lost, part of his long, dark past, always loved but often unremembered. "They sleep in my mind," he told Zoe, once, centuries and centuries ago, in another body, and he thought that was a good thing, a comforting thing. Now, he hates the idea. He doesn't want to forget.
River Song is coming, with a love he knows will end in death, foreordained and foreknown, and he wants no part of that smug, infuriating woman (intriguing and oddly hypnotic though she was). And yet…he can feel the shadow of his next self, and that man, he knows, will not be quite the same man who was willing to turn space-time inside out to save Adelaide Brooks (maybe that's a good thing, a traitor voice whispers, and he stamps it down). He will become someone capable of loving River Song in the perfectly clear, detailed knowledge of how her life will end, without trying to change that fate. He knows he will, because she made it clear that he already had. He doesn't want to become that man.
He feels almost like an adolescent of 200 again, raging against the settled calm of his elders, against the idea that one day he would see the world from their point of view and no longer from his own. He left Gallifrey so that he would never become like them, but he can't leave his own body. His next voice (he can already hear its echo in his mind) will call what's coming to claim him common sense, but this one denounces it as numbness and insensibility. He doesn't want to grow up.
This personality was made for Rose, longs for Rose, refuses to let her memory go. Even though the man he is can scarcely be stable or complete without her, even though he has made mistakes, terrible mistakes, out of this mind's passion, he will not relinquish the connection with her that this form symbolizes. These hearts are broken in a dozen places, first by her loss and then by many more, and it seems to him that to restore them to health, to do to them in one blazing instant what takes a human a decade, would be cowardice, would wipe away himself. If he could do it, if he didn't think Rose (and Martha, and Donna, and Astrid and especially, especially Adelaide Brooks) would call him a coward for it, he would refuse the regeneration. To him, it's death. He doesn't want to go.
Later, when an older, wiser, saner man wears a younger, dafter body over that soul, he calls it healing. He doesn't want to go back to what he used to be.
This has actually been sitting on my flash drive for almost six months, just waiting to be touched up and sent out into the world. Its actual origin, however, was a fight I had with my mother when I was sixteen. I was just adult enough to know that most children eventually come to agree with their parents and just child enough to really, really hate the idea. I remember vividly how it felt to imagine losing all the anger that seemed so important at the time, and that's how I've always understood 10's fear of regeneration.
TL;DR 10 is kind of a teenager. Anyhoo, I'd love to hear from you if you liked, and especially if you didn't (if you feel that this piece was too rambly-a concern of mine-feel free to review with just the word "rambly" and I'll still be glad to hear from you).