The excerpt from the story that supports the conclusion that the narrator is humble is:
" . . . I was not smart enough to pay attention to my balance, which I lost."
This sentence implies that the narrator is aware of their own limitations and doesn't overestimate their abilities. They acknowledge their mistake and accept that they are not smart enough, which is a humble attitude.
The other sentences don't necessarily imply that the narrator is humble, but rather provide more context about the story. In the first sentence, the narrator is describing their attempt to perform a figure skating move, in the second sentence, the narrator is describing the need to explain their appearance to new people, and in the last sentence, the narrator is describing the party they attended and how everyone looked great.