Leaders must be lifelong learners. Warren Bennis has taught that leaders must continue to deepen their inner world, cultivate the value and perspective of their life, and refresh their knowledge. I think that sometimes we learn material at a very cursory level, perhaps from a book. Later in life, we experience the truth of an earlier lesson, and suddenly we have something personal to talk about. If we continue to work at it, our knowledge goes even deeper, the leader has multiple lessons from life. The cumulative lessons help a leader confirm the truth from life and develop a more nuanced understanding. 

Who are the wise people in your life?

My guess is that the people you respect have wept, agonized, possibly even spilled blood to earn their life lessons. If they have substance, they have changed on the inside. Leaders have become wise people. The path to leadership is one that simply hurts.