First thoughts

I must say that I feel as though I know exactly what the narrator is talking about but based on everybody else's confusion, maybe I just THINK I do. Never the less, here's what I believe so far.
The narrator starts off by introducing himself as a spiteful man, "I am a sick man... I am a spiteful man. I am an unattractive man. I believe my liver is diseased." (Page 1) which leads me to be on guard for the rest of his story since spiteful people enjoy bringing pain or confusion to others. Saying this, I trust there to be a major turning point later on in the narrative or maybe his infliction on the reader is simply the impossibility of following his thoughts.
As far as his discussion, I am almost certain that this man is talking about spiraling depression, taking into account the negative emotions that lead further into darkness which he so thoroughly describes. "The more conscious I was of goodness and of all that was "sublime and beautiful", the more deeply I sank into my mire and the more ready I was to sink into it altogether." (Page 4) Depressed people can't grip onto happy moments for more than a second, and let any trace of bliss slip away from them, only forcing them to slip into deeper sadness. Now, upon reading this, I thought he was talking about himself and that he in fact had gone through some traumatic experience, leaving him to deal with his mind, because only someone who has been scarred previously in their life could have this kind of thought pattern. Yet, I was wrong and right at the same time. He later admits "I have not received a slap in the face" (page 8) and that in fact he was talking on behalf of the others who have gone through pains. Therefor, I was right in the sense that he was speaking about the depression that over comes someone's like after "a slap in the face" but wrong in the sense that I believed he was talking of himself.
However, I must keep in mind that he did admit to being a spiteful man in the beginning so it's probably best to predict for things to not be as they seem.