Think of a failure or a mistake that you had made and describe it. Tell what you learned from it and why it was important for your job. It should be related to at least one of the following: teaching, education, management or research.
You can start speaking in this way:
I think that a person who never made a mistake and never failed will never be able to achieve anything in his or her life. In fact, we discover and create by trial and failure and in this way we gain experience... [Add something from your personal life experience].