I think doing kata is like taking the slow boat to China.
It may be useful when you're sparring in a controlled setting with another karataka, but if you tangle with someone who is proficient at jui-jitsu, or a good boxer who knows how to distance himself properly, or even a smart street fighter, and try to use kata, you're gonna get smoked, and fast.
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Insert profound martial arts quotes or tough guy phrases here.