This chapter traces changes in the author’s teaching beliefs and practices over a year as an in-service English teacher at a Japanese high school, marking approximately 10 years of teaching experience since completing their master’s degree. It explores how an actual high school teacher plans, practices, and modifies their lessons according to the revised curriculum guidelines, their students’ needs and motivations, and their teacher beliefs based on a reflective journal. The author used a different method for the new 2023 school year—poster presentations—that better fit the new curriculum guidelines and required active student participation. However, after interaction with the students, the author changed their approach and subsequently adopted a different method, Jigsaw Retelling, which is an enhanced version of their original teaching style, incorporating the jigsaw method into retelling. Over the year, the author’s teaching style underwent several modifications. Unexpected ideas, combined with previous expertise, led to creative leaps for new methods. However, as the author implemented the new approaches, the students’ reactions and actual classroom situation influenced their teaching, causing them to adjust the lessons to accommodate their students’ needs. This paper clarifies such changes and offers insight into what constitutes growth for language teachers.