This week's Parsha, בהעלותך, describes the humility of Moshe. I have often quoted that there is a direct correlation between greatness and humility. The more humble a person is, the greater he is. And conversely, the more arrogant a person is, the smaller he is.
The Maharal expresses this idea in a beautiful fashion. Hashem in His abundant wisdom created man in such a way that he would strive towards perfection. The soul placed in man, would long for an attachment to his Creator. He would achieve great spiritual joy by gaining more of an understanding of G-d's essence.
As he continues in this spiritual quest, the more he learns about Hashem, the more he realizes that whatever he has learned is only a drop in the bucket of Hashem's awesomeness.
This was Moshe Rabbeinu. He knew Hashem in the most intimate way known to man. Yet, the more he understood, the more he knew how limited man was in terms of G-d. This knowledge only made him more humble. This humility is what made Moshe Rabbeinu the greatest man who ever lived.