I need you to know
He entered the TARDIS without a word and looked around remembering the first time she was there... they were there... together. All those moments now over and frozen in time... they would never happen again, not that way, not with her.
He sat down on the old couch still holding her jacket. It still had her smell, souffles... she made him one this morning and he had promise to eat it at the end of the day... But what was the point now? She was gone... gone forever... she was never gonna coming back and for the first time since his regeneration he cried. He cried for what it seemed like hours with no one around to see or hear him... no one except the TARDIS.
He walked around for the longest time finally starting to realize all the things he should have said to her but never really had the courage to do it. To tell her how much he loved her souffles. To thank her for never giving up on him even when he, himself, wanted to. To tell her how much in fact he loved her hugs. And above all to thank her for being who she is... was.
In that moment something started beeping in the TARDIS and he rushed to the screens but nothing was there, he didn't understand. That usually didn't happen. That's when he heard them, those words that he never thought he would hear again, no after Trenzalore - "Run you clever boy"-, he turned around and saw Clara Oswald, standing in front of him once more, like an echo. But it wasn't an echo, no, that was impossible. But after all, Clara was always given to the impossibilities. He reach out to her and when he tried to touch her face once more that's when he realized... it was an interface. A message left by her. She looked younger, maybe she had predicted that moment a long time ago.
"Play the message", in that moment he looked down to her jacket, he didn't even knew he was still holding it. He was invaded by feelings like anxiety and fear which reminded him of all those nights in the barn when he was a little boy in Gallifrey. And so the message started playing - "Hello Doctor. If you're listening to this that means I'm... I'm... dead." - that's when everything became more real to him and without a choice he started crying again, - "I don't know how it happened nor when will it happen, but I want you to know... no, I need you to know that it wasn't your fault. Whatever happened it wasn't your fault. So please don't blame yourself, ever. And above everything else I need you to know that I love you and I always loved you. And I don't mean I love you in a boyfriend-ish way, no... I mean I love as my friend... my best friend." - The Doctor kept crying now holding her jacket closer to his chest, because that was his only way he could feel her again, - "And finally you deserve to know that the happiest moments I ever had were spend with you. Just you. So thank you for that. And please, let Danny know what happened, whether we're still together or not... Just tell him. And please, don't ever, ever be alone again. Find someone. Goodbye Doctor, my impossible boy.".
The message had reached it's end. The Doctor stood there looking at the space where Clara was once projected. He didn't moved, not until he felt a piece of paper in his pocket. How did it got there? He wondered... but after all, how does anything ever gets there? He opened it and a smile instantly lighted up his face - "Don't forget the milk for the souffles" - Clara must had written it this morning. And so he went to Earth to full fill Clara's last wishes: talk to Danny and buy milk.
And as a whisper that no one around would hear except the TARDIS he said "Watch me run, Clara Oswald".