FYI, this is set at the end of the End of Time. As you'll no doubt notice, it ends up a bit differently. Especially later.
The Doctor staggered into his TARDIS one last time, the song of the Ood echoing behind him. His companions were safe, all of them: even Jack seemed quite happy, not letting the guilt of slaughtering his grandson distract him from flirting. The Doctor winced as another convulsion passed through him: it was time. Regeneration, and the first one truly alone. He'd had his companions before, wide-eyed and worried: Ben and Polly; the Time Lord High Council (something of an exception, yes); Sarah-Jane and the Brigadier; Tegan, Nyssa and Adric; Peri; Mel; Destrii; Rose. Admittedly there had been that one time in the hospital, but he'd been technically dead at the time and tended not to talk about it.
This time, however, he was alone. He turned his hand over, watching the faint beads of light begin to form on his palm. His first time alone, and he wasn't ready at all. He looked around at the TARDIS, his sole companion in his newest ordeal, and sighed inwardly. It was too much to be here at his age, on his own and about to die. He needed someone with him, to keep him together, prevent 'The Time Lord Victorious' from emerging again. His greatest victories were thanks to his companions' initiative and compassion. His hands were glowing now, visibly, and he couldn't hold it off any longer.
"I don't want–" A movement in the shadows caught his eye – there was something in the TARDIS, hiding behind the coral. But how could anyone have got in without him noticing?
Then the light exploded and the TARDIS shook violently. He could see nothing, but couldn't shake the figure that still flitted in front of his eyes. A strangely familiar figure who was now walking toward him. Black hair, small angry eyes, and a beard...
"This is the end, Doctor!"
The rest was silence.