Answer:
The narrator feels confident in that moment.
Step-by-step explanation:
This passage was taken from the short story "The Tell-Tale Heart", by Edgar Allan Poe. The narrator insists with eerie confidence that he is sane. That insistence is precisely what proves him mad, especially when he admits to having killed a man because he could hear that man's heart beating. His confidence comes from the fact that he was able to premeditate the crime. He believes he wouldn't have been able to plan it in advance had he been mad.