A/N: Have had this floating around my head since I saw 'The Runaway Bride' and then 'Smith and Jones'. I would assume it's generally understood that the Doctor's had some time away from it all, thinking things over, and deciding where his place in the universe really is.
The Doctor walked around the TARDIS console glumly, the cacophony of sounds an assault to his grieving soul. Instead of the familiar and loved sounds of his companion puttering around the TARDIS, all the little noises became deafening; the whiz-hum of the engines, his own footfalls, and the lonely beating of his hearts. That peculiar sound of a person crying in silence was not evident; he had cried many times in his long life, and tears could no longer help wash away the feelings burning through him. Rose was gone, and no amount of tears – even those from the last of the Time Lords – would ever bring her back.
The Doctor sighed deeply, and dropped heavily into the captain's chair. The vid-screen on the main console showed stars and galaxies tumbling and reeling past; no beloved face, no landing site for another madcap adventure. What will I do now? he thought. I am the last of my kind. All that I have loved, I lost. There are no others like me that I may travel with; any new companion will end up being left behind, just like all the others. His thoughts circled endlessly, wracked with guilt and pain. Could he do that to another soul again? Even in his loneliness, could he justify the breaking of another's heart? To be left behind and 'forgotten'? Could he face helping worlds and races without hope of companionship?
He flung himself from his chair in anger, driven by motives and desires that clashed incessantly. As the last of his kind, the Doctor felt obliged to carry on his travelling, his thirst for knowledge ever-present, the drive to help and to heal still strong. But as a man alone, he hungered for the pain to stop. His face hidden in his hands, the Doctor wept silently. Tears, he felt, were almost useless to him now, but perhaps they would tire him enough that sleep was necessary, dark and dreamless.
He sank to the floor, resting his head on bent knees, arms wrapped tightly around his legs as he rocked, the sound of sobbing echoing back from the walls.
He was alone.