habit becomes second nature ❍ 余少好抄书，……～，不觉笔倦。(《南史·王筠传》)I was fond of copying books when I was young…As habit becomes second nature,I never got tired of writing.
习与性成xí yǔ xìnɡ chénɡ
性：性格。长期习惯于某种生活习惯，就逐渐养成相应的性格。habits become one’s second nature, habits make things natural