The author is deeply embarrassed the next day in school because he feels self-conscious and ashamed of his actions. He is particularly embarrassed because of how he behaved in front of his classmates the previous day, which he now views as a mistake. He fears how others might perceive him, and this fear of judgment makes him insecure about his reputation.
The words that show his fear and insecurity include expressions like:
These phrases suggest that the author is not only embarrassed but also deeply fearful of how others perceive him, emphasizing his feelings of insecurity.