The problem with a one-person show is that it feels awkward to observe a single man talking to himself over a long period of time. To circumvent this Steven Moffat chose to steal a device from one of his other projects, Sherlock, and switch the point of view to within the Doctors head. This is a smart thing to do as it gives us a way to hear the Doctors thoughts. It makes sense that he talks to himself within his mind and that he would picture himself in the TARDIS as that is his place of safety. The return of Clara is startling and haunting as she is mostly portrayed from the back and replies by scratching on a chalkboard. Her loss is felt even more keenly when we are presented with the Doctors grief-stricken vision of a person who now lives only within his memories. It is fitting that Clara is most alive to him when he imagines her exhorting him to get off his ass." That is exactly what Clara would have done and its a beautifully wrought and bittersweet moment when we are allowed a brief glimpse of her long lost face.