It could be because he possesses the temperament of an artist stuck on perfection. If something fails to meet with his set of standards, he is gloomy and miserable and will not utter one word.
因為他有凡事要求完美的藝術家脾氣，只要事情做得不合他的標準，就可能幾天悶悶不樂，不說一句話。