Tim Irwin writes in “Impact: Great Leadership Changes Everything”:

In working with thousands of leaders over many years, I have observed that they rarely fail because of lack of competence. Clearly competence is necessary, but it is not sufficient to be a great leader. We must also have a strong core. The word "core" has become a major idea in the physical development of athletes and others interested in fitness. Core includes all of the muscles of the midsection. The core muscles stabilize the entire body and are prime contributors to strength and coordinated movement. Athletes in just about every sport focus on developing their core muscles because it has proven to make them so much better at whatever sport they play.

When our core is intact and congruent, others experience us as authentic, humble, and trustworthy. When our core is compromised or conflicted, others experience us as arrogant, self-serving, and insecure. No matter how artful their style or competent their actions, every failed leader I have studied had a malfunctioning core—it had been broken in some significant way.