Yes, I think that we can agree - we are just coming at questions from different directions. I have no knowledge of brain chemistry. Too bad your novel is only available in Greek!
Strange Life of Ivan Osokin
Plot summary
When the protagonist realizes that he can recall having lived his life before, he decides to try to change it. But he discovers that because human choices tend to be mechanical, changing the outcome of one's actions is extremely difficult. He realizes that without help breaking his mechanical behavior, he may be doomed to repeat the same mistakes forever.