Martial artists are people who live their lives with ikigai (生き甲斐) or a sense of purpose.
In the Book of Five Rings, Miyamoto Musashi wrote, "Do nothing which is of no use."
With Musashi's assertion in mind this leads us to believe that we must live our lives for something. That something is ikigai. Someone poignantly defined ikigai as "The reason that gets you out of bed in the morning."
The average person is someone who is usually caught between two masters: one who dictates how they use their time and the other which uses that time up. Martial artists are people who live their lives with ikigai and thus choose how they want to live their lives.
With an understanding of one's ikigai then we can understand things like gaman or perseverance, isshokenmei or hard work and konjo or will-power. These three things powered by ikigai are what makes a martial artist a martial artist.