What did you learn this year?
However, students weren't alone in class. You were there too.
Did you take the chance to get feedback from them about the class? Did you include their feedback as part of your year-end professional reflection?
In some format, you probably asked them, "What did you learn this year?"
For the student-centered lead learner (yes, I mean you, the teacher), the same question applies.
What did you learn this year?