The narrator starts out tired and sad, weary of life and the misfortunes he has experienced. When the raven arrives, he initially thinks of it as kind of a silly bird, a diversion - one that can actually talk. But then he gets it into his head that the raven is as wise as Athena ("Pallas") and can answer deep mysterious questions for him - even foretell the future. So the narrator becomes more and more frantic as the answer to each of his questions to the bird ends up being "Nevermore." This is not good because he is asking questions concerning his lost love, Lenore, and whether he will ever be happy again, whether they will someday be reunited, etc., so each time the bird answers "Nevermore," the narrator becomes more and more frantic and upset, until he is actually shrieking at the raven.
So the narrator starts out weary and quiet and ends up frenzied and upset by what he ends up deciding is an evil bird.