From the Hagakure:

A certain swordsman in his declining years said the following:

"In one's life, there are levels in the pursuit of study. In the lowest level, a person studies but nothing comes of it and he feels that both he and others are unskillful. At this point he is worthless. In the middle level he is still useless but is aware of his own insufficiences and can also see the insufficiences of others. In a higher level he has pride concerning his own ability, rejoices in praise from others, and laments the lack of ability in his fellows. This man has worth. In the highest level a man has the look of knowing nothing.

"These are the levels in general. But there is one transcending level, and this is the most excellent of all. This person is aware of the endlessness of entering deeply into a certain Way and never thinks of himself as having finished. He truly knows his own insufficiences and never in his whole life thinks that he has succeeded. He has no thoughts of pride but with self-abasement knows the Way to the end. It is said that Mast Yagyu once remarked, 'I do not know the way to defeat others, but the wayto defeat myself.'

"Throughout your life advance daily, becoming more skillfull than yesterday, more skillful than today. This is never-ending."