Out of sight, out of mind. 眼不見，心為靜。

Out of office, out of danger. 無官一身輕。

Out of debt, out of danger. 無債一身輕。

One's words reflect one's thinking. 言為心聲。

One swallow does not make a summer. 一燕不成夏。

One never loses anything by politeness. 講禮貌不吃虧。

One man's fault is other man's lesson. 前車之鑒。

One hour today is worth two tomorrow. 爭分奪秒效率高。

One good turn deserves another. 行善積德。

One false move may lose the game. 一著不慎，滿盤皆輸。