Once in a while, when Clara is sleeping or visiting her home, the Doctor likes to wander around the TARDIS.

He doesn't always means to, but he always ends up in the same room. If anyone else would look inside, he will see shelves of random items, nothing of great importance, nothing at all in comparison to the infinity of the ship, but for the Doctor, that room means everything. Because they are not random, not to him. To him, every item represent a friend he's lost. And The Doctor has many friends, but they all leave him, in the end. Some by choice, some not. But they always leave, and they all leave something behind.

So he sits there, only when he's alone, and he goes through those items.

A little toy TARDIS, because once, he met a little Scottish girl. He became her imaginary friend, she became his family.

A box full of hats, because he never got to take his best friend to that planet of the hats she was ready for, and now he never will.

A sonic screwdriver, one that he's never used, and never will. Because this one is not meant for him, and this story is not over yet.

A key to the TARDIS, only ever used by the girl he kept disappointing, that saved the world and moved on.

A sonic blaster, for the con man that became a hero.

And a jacket, which he always saves for last, because he loved her, and she ended up with someone else.

There are other things there as well, so many things. The TARDIS keeps all those things in the room, always making sure that there will be something to keep and nothing is ever lost. He doesn't like being in that room. There are too many memories inside, but the TARDIS always leads him there, because she knows. She knows that he has to remember, so he can move on, and always know that he is loved. By so many and so much.

When the Doctor leaves the room, he goes back to Clara, he puts a smile on his face and asks her where she wants to go next. Anywhere, all of time and space right outside those doors. That was what he promised her.

To himself he promised, not her, not again. Because he doesn't like that room, and he doesn't want to add to it.