Both of these quotes show characterization used by Poe. The narrator is the main character, and it must be noted that this story is being told in hindsight, trying to convince the reader/audience that he is not "mad", as they all believe him to be. He invites the reader to "Hearken! and observe how healthily - how calmly I can tell you the whole story"
The recollection of all of these facts that create this story are to show how he took such care and caution and possessed such foresight when planning and committing the murder. The first quote is commenting on this and his cunning to conceal his intent. Once again, he believes that this characteristics prove that he cannot be "mad".
The second quote shows his patience when fulfilling his goal. He was determined and willing to remain calm and work slowly to ensure that he would not be caught. Once again, qualities not typically associated with those who are "mad".