Most of us get better at living as we go. There comes a moment, which may come early or later in life, when you realize what your life is actually about. You look across your life and review the moments when you felt more fully alive, at most your best self. They were usually moments when you were working with others in service of some ideal. That is the agency moment. That is the moment when you achieve clarity about what you should do and how you should live.
