If a warrior is not unattached to life and death, he will be of no use whatsoever. The saying that "All abilities come from one mind" sounds as though it has to do with sentient matters, but it is in fact a matter of being unattached to life and death. With such non-attachment one can accomplish any feat.
Meditation on inevitable death should be performed daily. Every day when one's body and mind are at peace, one should meditate upon being ripped apart by arrows, rifles, spears and swords, being carried away by surging waves, being thrown into the midst of a great fire, being struck by lightning, being shaken to death by a great earthquake, falling from thousand-foot cliffs, dying of disease or committing seppuku at the death of one's master. And every day without fail one should consider himself as dead.
In the words of the ancients, one should make his decisions within the space of seven breaths. It is a matter of being determined and having the spirit to break right through to the other side.
Do not, my soul, seek immortal life, but exhaust the limits of the possible.
Remember that man lives only in the present, in this fleeting instant; all the rest of his life is either past and gone, or not yet revealed. Short, therefore, is man's life, and narrow is the corner of the earth wherein he dwells.
True happiness is to enjoy the present, without anxious dependence upon the future.