"So maybe you aren't special. Y'know who else isn't? A shop girl from London who never got any A-levels. She lives with her mum, who's insufferable and tatters on about everything, has a boyfriend that's pretty stupid, and doesn't do much all day other than work in the shop and go down to the pub. Doesn't sound special, does it?"
The Doctor arched his eyebrow.
"But she saved my life. She caused a paradox and then corrected it herself. She kickstarted an alien life form I thought was completely eradicated, just by touching it."
He smiled very slightly at the thought of her.
"So then there's Mary Winchester. And maybe you're right and your not meant to do anything that special. Maybe you don't save the world. But maybe you have to be there so somebody else CAN."
She'd been sent back. So had her sister. Why?
"Mary, what do your mum and dad do? You said the angel sent you back for family. Why is your family special?"