There is no shortage of books written about the essence of Budo, but it is preferable to regard most of these as autobiographies of people with experience. We must not lose sight of the mystery zone of budo/bugei/strategy in which if there is too much knowledge (chishiki 知識) it becomes foolishness (chishiki 痴識). Moreover, we must consider the fact that even the people who wrote about “essence” had experienced defeat in fighting matches. Nevertheless, these defeats became good transmissions. Indeed, it is when the defeated realize their mistakes and errors and transmit this understanding to future generations that the truth of Budo is inherited.
-Masaaki Hatsumi, The Essence of Budo