By slow degrees, these feelings of disgust and annoyance rose into the bitterness of hatred. I avoided the creature; a certain sense of shame, and the remembrance of my former deed of cruelty, preventing me from physically abusing it.
This description of the narrator’s emotions comes after he brings home the second black cat. Although he brings the cat home believing it will allay his guilt for murdering Pluto, it does the opposite instead. The disgust and annoyance that the narrator describes here signals his inability to handle his guilt from murdering Pluto. At this point, the shame he feels in remembering Pluto may keep him from hurting the second cat, but his desire to rid of those feelings will eventually win out.
It did not make its appearance during the night — and thus for one night at least, since its introduction into the house, I soundly and tranquilly slept; aye, slept even with the burden of murder upon my soul!
The narrator here describes how after he murders his wife, the black cat disappears. The apparent lack of guilt the narrator feels here is at first shocking, especially as he seems more concerned with being rid of the cat. However, the reason why the narrator wanted to be free of the cat in the first place was because looking at the cat made him feel guilty. Metaphorically, without the cat there, the narrator can tamp down his remorse, even sleeping knowing that he has murdered his wife. However, the narrator won’t be able to repress his guilt for long.