The point is, I’m seeing a lot of people assuming that the monster isn’t real just because THAT experience in the LIFE OF THE DOCTOR was not real.
But that doesn’t mean the monster is not real. The thing, the big point of the episode (for me at least) is the fact that the monster, or rather creature (who apparently is someone scared and lonely, but who cannot trust anyone), may or may not be real. And since if it’s real we will never know (because it is perfect in hiding), we can’t live in fear and despair, we need to get these feelings and make something good of it. We continue to live the best we can, being brave, happy, listening to our own dreams… And sometimes we talk to ourselves for protection, to have someone to listen to, or perhaps to let it know that the fear makes companions of us all and that we all make it our companion as well… even if you’re a (future) Time Lord of the great planet Gallifrey in the constellation of Kasterborous,