The mind must always be in the state of 'flowing,' for when it stops anywhere that means the flow is interrupted and it is this interruption that is injurious to the well-being of the mind. In the case of the swordsman, it means death
Mushin is achieved when a person's mind is free from thoughts of anger, fear, or ego during combat or everyday life.
Once mushin is attained through the practice or study of martial arts (although it can be accomplished through other arts or practices that refine the mind and body), the objective is to then attain this same level of complete awareness in other aspects of the practitioner's life.