I know this is ridiculously short, but I thought some may enjoy this piece of agony. Suggestions are always welcome. Please read & review.
Set after the Doctor has returned Donna home and has just lost his best friend at the cost of saving the world, or rather, the Universe. He decides that he cannot face finding another companion, only to lose them again, breaking his already shattered hearts.
The Doctor was alone. He had always been alone, since he had ended the Time War, but never had he felt as truly isolated as he did now. Rose, Martha, and now Donna. Surprisingly, the loss of Donna stung the worst, more even than knowing he would never see Rose again. She had been the one to make him realise that any life saved amidst slaughter was worth the price of being present. She had shown him that even though he had lost a family, it didn't mean he was exempt from forming a new one. She had not shied away from the Universe, instead she had remained steadfastly human, trying pointlessly to put it back in its place. She had pulled him back from the edge so many times, and hadn't even known. Now she never would. Maybe it wasn't surprising that he missed Donna most after all.
Doctor? He looked up, searching the dim TARDIS for something. Doctor, where are you? He froze, recognising the unmistakable voice. I promised that I'd travel with you forever. Tears stung the Doctor's eyes, and he stopped searching for a body to put the words to. I wanted to see the Universe. She wasn't there, she could never be there again. Oi, are you listening to me Spaceman?! A sob forced its way out of his throat. No one else would think to call him that. I'm sorry. I'm so sorry. Finally, he couldn't take it anymore, and the tears streamed down him face, and the sobs racked his thin frame. A tall streak of alien nothing, you are. He leaned against the central pillar, trying to pull himself together without success, as the memories kept on coming.