In an arguably poor-received way, Dexter ended in a very odd way. Our favourite serial killer is now a lumberjack in wintery... wherever. The question comes back to why? Why does Dexter choose to seclude himself in such a fashion when everything was bumpy, but working out well enough?
Because Dexter now realizes that he is the one who is responsible for Harry's suicide, Deb's condition of being on life support, Rita's death, and Vogel's death. He can't bare it anymore. He now thinks that everyone he is comes into contact with will be destroyed the same way — that's why after killing The Brain Surgeon he stopped Deb's life support system to free her from anymore pain and even decided to commit suicide too, leaving Harrison in the care of Hannah McKay.
Somehow, he survives and shows up as a lumberjack. This means he survived, but still didn't want to go to Hannah or Harrison in order to save them from his darkness.
The last sight of Dexter eyes were still very arguable making a point for an open end.