This is based on a request from kenzcraw. I know it's not exactly what you wanted, but this is what I came up with so I hope it's okay.

Summary: The Doctor comes to terms with the fact that he can't save humanity or Clara this time in the middle of the episode.

Forest of the Night

"Alright come on team!" PE yelled at Clara's 'gifted' children. They flowed around the Doctor excitedly and each found a spot around the edge of his TARDIS. He watched as they pulled at the miraculously thick vines, chattering enthusiastically amongst themselves. Clearly, these small humans couldn't grasp the gravity of the situation; their planet was about to be destroyed and they were swinging around on vines gleefully like that ridiculous ape-man cartoon. He half expected one of them to yell and beat their chest.

The Doctor and Clara joined the children in their efforts, but he was still lost in thought. He was far from excited at the prospect of being trapped in his TARDIS with a bunch of whining kids; there was sure to be a lot of crying and snotty noses when they finally caught on. Still, he could find them all a new home soon enough. Then maybe Clara would move in with him and they could go adventuring full time without her pesky soldier boy interrupting them so often.

"When they're done, you need to get in your box and go," Clara's soft voice interrupted his daydreams.

"We're all going. We're taking the kids," he replied, continuing to pull at the thick vines.

"Go where?" Clara asked. He turned to look into her face in confusion. "What are you going to do with them? Leave them on an asteroid? Put them in a space academy for the gifted and talented? They just want their mum and dads. And they're never gonna stop wanting them." She turned away from him, ponytail swishing against her grey sweater.

The Doctor's hearts sank. She was right, of course she was. He couldn't save these children by taking them away from their parents and their home. Visions of towns named after the Human's great savior dissolved in an instant. But the human race didn't have to die out; he still had his time machine; he could still save someone, just like Donna had insisted on so long ago in Pompeii. He would save Clara, of course, but she wouldn't leave her boyfriend behind. If it meant saving her, and giving the human race a chance to repopulate, he could manage with PE on board as well. He leaned down to whisper in Clara's ear "I can save you and Danny."

But Clara was shaking her head again. "Danny Pink will never leave those kids as long as he is breathing."

The Doctor furrowed his eyebrows in concentration as PE and his team retreated, saying something about another 'selfie'. Fine, he wouldn't be the savior of the humans. But he and Clara could still go on their adventures. She would be upset for a while, but he would help her move past the loss of her world. He had survived on his own, but she wouldn't have to. She would have him.

"I can save you," he tried desperately.

"I don't want you to."

"What, you don't want to live?" the Doctor growled, trying to appear angry to hide his fear.

"Of course I want to live," Clara snapped back. "I just,"

"What?" the Doctor asked, shaking his head.

"Don't make me say it," she begged, remaining as stubborn and uncooperative as ever.

"Say what?" He insisted.

"I don't want to be the last of my kind."

Oh. Of course. She didn't want to be like him, a lonely man in an old box. She didn't think that the two of them together would be enough to make it worth living with the grief. She would die rather than turn into someone like him.

"Then why did you bring us all here?" the Doctor asked, his voice even more gravely than usual from the emotions swelling his throat closed. She had lied; she'd gotten his hopes up and put fantasies of saving the day once again in his head. This must have been what it felt like when those passengers on the Orient Express realized that the Doctor couldn't save them, just as the Mummified soldier appeared to steal their life away: this moment when the false hope melted away and left behind an aching cavity in his chest.

Clara smiled sadly. "Because it was the only way to get you back to the TARDIS. Make you think your saving someone. Well you know what Doctor? This time the human race is saving you," She took out her key and opened TARDIS door, which creaked inwards solemnly. Clara gestured at the opening, just as he had done to her so many times on so many worlds.

He looked into her brown eyes, hoping to see some sign of doubt, any shimmer of uncertainty that showed she could be persuaded to stay with him, to live on. There was none. "Make it worthwhile," she told him. It was a very firm, very final statement that left no room for argument.

"This is my world too," he reminded her, quoting her angry words from their moon debacle at her sincerely. "I walk your earth, I breathe your air."

"And on behalf of this world, you're very welcome," Clara stated. "Now go. Save the next one."

He knew she was right. Somewhere, his logical mind knew that Clara was telling the truth; he couldn't save Earth, and he couldn't doom her to the same sad existence that he had suffered through for hundreds of years. He could either resign himself to die here – for the final time – or he could go on and save other worlds in the name of Clara and Earth.

The Doctor spun suddenly; there was one last thing he needed to do before he abandoned his second home forever. "Maeve!" He called, watching the little girl scamper over, leaves crunching softly beneath her feet. "I'm sorry that I couldn't help you."

"You helped me loads! I thought it was all my fault, I feel much better now," she answered. "Are you going to get rid of the forest?"

"How do you get rid of a flame proof forest Maeve, eh?" Clara asked with false lightness. She brushed pasted the Doctor's shoulder and led the small child towards the group, refusing to glance back at him. The Doctor turned his back on his friend, brushed aside the vines in an angry sweep of his arm, and slammed the door of the TARDIS behind him in one fluid movement. He smashed a few levers into place and his TARDIS disappeared, wheezing a final goodbye to the world he had grown to love too much.

So yeah, a bit more angst and bleakness than my other chapters; I hope it's okay. Also, none of the dialogue is mine, since it's all from the episode.