It should be noted that there are two types of knowledge: the factual information that can be acquired by formal education and real-world practices, and knowledge of one's own "inner" world. It is the second category that uniquely establishes the standard of real leadership.
"Know Thyself" is to understand your inner world, your bright and dark sides, your personal strengths and weaknesses. Self-comprehension is a fundamental precondition necessary for real leadership.
Sayings based on great wisdom, such as "Know Thyself," have one thing in common, regardless of the time and place in which they occur: they are encouragements to engage in conduct that is demanding and out of the ordinary but nevertheless offers prospects of great reward.
Coming to "know thyself" in a modern sense of the phrase is an immensely difficult task. Even for those inclined to seek deeper meaning and understanding, the volume of distraction is such that very few are able to engage in anything approximating a meaningful program of self-interrogation.
It is essential that the would-be leader commit to an agenda of spirited self-indictment, because the most lethal distortions come not from the lips of our opponents or competitors. They tend to flow, instead, from our own hearts.
"Knowing thyself" means bringing a fresh transparency to our hidden motives and identities.
In "THE TEN GOLDEN RULES OF LEADERSHIP: Classical Wisdom for Modern Leaders," the authors present a compelling case for a deeper and wider understanding of leadership as a challenging calling distinct from management. "Leadership," in the authors' estimation, "is an uncommon composite of skill, experience, and ripened personal perspectives regarding the nuances and complexities of life. Only those men and women who have cultivated a carefully conceived philosophy of life are capable of genuine leadership."
Source: M. A. Soupios: The Ten Golden Rules of Leadership: Classical Wisdom for Modern Leaders
Women, Know Thyself: The most important knowledge is self-knowledge.