‘Kangeiko’ (寒稽古) a Japanese word meaning; “cold training.” It is special training, in various forms of budo/bujutsu, in which practitioners endure training in the cold. This mid-winter practice is meant to strengthen not only the body, but the mind.
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This concept is a special test of endurance training – forcing oneself to perform under difficult or even painful conditions. In theory, this strengthens the “fighting spirit” by helping us find our true limits and quietening the inner-dialogue that keeps telling us to give up.
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This idea of subjecting oneself to harsh treatment in order to strengthen the resolve owes its influence to Buddhism (in Japan, anyway). Ascetic monks would choose the coldest days of the year to set an example and demonstrate their piety.
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‘Kangeiko’ is conducted during the coldest time of day, usually before dawn or at dawn. As Shinto religion, “Shugendo” (Japanese mountain asceticism) and some sects of Buddhism incorporate ascetic practices like bathing in the sea/river or standing under a waterfall, with the aim of mental training, ‘Kangeiko’ in budo often incorporate such exercises.
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It is also marks the beginning of a new year, and therefore a new opportunity to improve technically and personally through the discipline of Budo training.
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The most important thing you can get out of ‘kangeiko’ is to give it your best and start off the new year of training with a positive attitude. Beyond that, take it as a chance to push yourself to the next level by challenging your body, or your mind, with more intensity than usual. Being outside your comfort zone will help you grow as a martial artist. 
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“We don’t rise to the level of our expectations, we fall to the level of our training.” – David Goggins
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