There's a reason the Doctor has always made an effort not to take too much notice of physical beauty. It's not because it will ultimately fade away, though he knows better than most that everything does in time. It's that he knows that, given the right object for his focus and half an opportunity, he could easily waste away all of his regenerations just taking in every tiny visual detail.
Light refracting through a stray raindrop hanging precariously off the tips of her eyelashes. Her skin glowing with a honeyed tan after their recent trip to the universally famous crystal beaches of Otepa. The teasing sparkle in her eyes whenever she grins. The brief flash of her tongue against her teeth, highlighting the tempting curve of her lips.
Rose's smile is more than capable of blinding him to everything else around him. And even though he's the only one of his kind left, which means that he has vital responsibilities that it would be completely irresponsible for him to ever think of just ignoring, she still frequently manages to dominate his attention even when he knows it will probably get them – and possibly the universe at large along with them – into serious trouble.
He finds that it's far too late to try to desensitise himself to any of that now, though. He's already long since fallen under that particular spell.
Besides, although her looks are undeniably captivating, they're hardly the only thing about her that has him tied in knots. He would never have invited her on-board the TARDIS in the first place if not for her flashes of brilliance, her interminable courage and desire for adventure, and her sense of humour, among so many other things.
And even all of those qualities combined together don't begin to describe all the reasons why Rose is so indispensably important to him.
He wonders whether she has even the vaguest concept of how easily he could get completely caught up in her and let her be his everything. That is, of course, right up until the moment when he cracks into a thousand pieces immediately after he loses her; he's not foolish enough not to understand just how inevitable that ending is for the two of them.
Words are usually his gift, especially in this current regeneration. Yet he can't seem to find any way to convey to her that she's significant enough to him that he has no intention of letting her go until she herself insists on it... at least without falling right into the obvious trap of his feelings, which he knows he can't risk. Instead, he's rendered effectively speechless, for the only words he can think to speak should never gain a voice. He would lose too much of himself in the telling.
The only way he can prevent that is for the possibility of any further embellishments to their relationship to remain far out of his reach. He can't seem to stop himself from wishing for more, but that's all he can ever do without hurting himself more than he can stand.
Not even a Time Lord can touch the stars without being burned.
~FIN~