What does Rainsford’s repetition of the word “nerve” in paragraph 170, paragraph 180, and paragraph 198 reveal about his character?

Rainsford uses the word "nerve" in the same way we would use the term "courage". He repeatedly reminds himself that he must not lose his nerve..... or courage. In context, we can infer that Rainsford is a brave man, whose bravery is faltering..... he will not, however, allow that to happen.