"On the physical level a karateka needs to maximise his strength, speed and flexibility. In order to do this hard work is necessary. It is also important to be able to suffer to some degree without complaint. Carl Jung, in his work The Development of the Personality observed, "There is no coming to consciousness without pain," and I think that is certainly true about the martial arts.
"Mentally I feel you need to develop and maintain an open enquiring mind, what the Zen people refer to as shoshin or beginner's mind. Shunryu Suzuki said: "In the beginner's mind there are many possibilities; in the expert's mind there are few." Karate should be the art of the open mind as well as the art of the empty hand." - Harry Cook