Commonly-used American Slang
スラング: keep 〜 cool
keep 〜 cool  =remained calm, calmness, composure, to remain calm and in control 
意味: 落ち着いている 冷静 
lose one's cool 冷静さを失う。
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  keep 〜 cool 例文:
 - He kept his cool when his house went foreclosure.
彼は家を担保に取られても落ち着いていた。 - He lost his cool when he found out that his wife was cheating. 
彼は妻が浮気をしている事を知り、冷静さを失った。 
keep it real ← keep〜 cool → kick