During their first confrontation in "Rikki-Tikki-Tavi," how are Rikki and Nag feeling?

Both Rikki and Nag are afraid during their first confrontation, and rightly so. Each represents a formidable threat to the life of the other. Nag hides his fear behind threats and bravado. He brags about his looks and his origins as having been specially created by Brahm. He spreads his hood in a threatening fashion. Despite this bravado, he knows mongooses in the garden are a death sentence for cobras. He shifts to a conciliatory tone, attempting to distract Rikki long enough for Nagaina to creep up behind him and strike.
Rikki is "afraid for the minute" when he sees Nag's display and hears his words. The innate courage and confidence of his species make him unable to remain fearful for long. He realizes mongooses are born and live to "fight and eat snakes," and his spirit rises to the challenge. He confronts Nag forthrightly for eating "fledglings out of a nest," allowing his anger and sense of justice to override his fears. 
As it turns out, Rikki is able to dispose of Nag, Nagaina, and their offspring. Nag's fear and Rikki's confidence foreshadow the eventual outcome of the story.