the strong will can pierce a stone.

" the man of strategy must have just such a strong will or unshakeable conviction because it is in this form of belief or faith that an unbelievably powerful strength is made manifest. without this kind of conviction, one's best efforts will come to nothing."

shugyo

I think it is good to push yourself to the extreme ; to push your mind and body to the point of imminent death has a purpose during time of war. The tradition of severe training (musha shugyo) in the martial arts aims to awaken inner power . however , when the appropriate time comes , change swiftly. This is "TENKAN," in other words ,being able to control yourself.
Hatsumi sensei,

The heart

No matter how strong one is or how hard one trains , One's heart only becomes darkened and darkens the heart of society when one tries to become master without these principles (Kaseichikusei, Banhenfukei, Bushinwa.)
T o see the shining power of the soryu (inherited style) and to know it and to know oneselfis to gain two hundred allies.

The direct mind

Understanding the mind and its working s is crucial development as a competent fighter.
The brain is a valuable self defense tool that is often overlooked in many martial arts training systems. Physical conditioning and technique memorization can take the practitioner only so far,
and the advanced fighter must go on to develope the qualities of awareness and detachment.
This detachment is an ability to figuartively back-off from activity in which you are engaged and observe the total picture of what you are going to do, you simply observe the attackers's actions froma defensive pose and react appropriately to his moves. instead of concentrating on beating your adversary ,you allow him to make the mistakes that will bring about his downfall.