Knowing that your whole life has been planned by someone else was definitely hard to swallow. By the time Number One returned to the Academy and began his usual plan, he couldn't be sicker of it. Everything he wanted to do seemed as if it was exactly what his Master wanted which made him want to do the opposite.
After Number One confirmed with Headmaster Blake that he never informed the main Academy about him, he completely lost trust in anyone who wasn't close to him. Any Academy Official or another student could be planted into his life with the goal of watching him.
The first few days were rough but Number One quickly recovered with new motivation pushing him forward. He stopped thinking about his Master's reasons and began working hard to get stronger. Only by reaching the minimum threshold of power could he actually take back his life into his own hands.