百胜难虑敌，三折乃良医
bǎi​shèng​nán​lǜ​dí, sān​zhé​nǎi​liáng​yī

learning from failure

百胜难虑敌，三折乃良医 (百勝難慮敵，三折乃良醫) bǎi​shèng​nán​lǜ​dí, sān​zhé​nǎi​liáng​yī
learning from failure
One gains more insight and expertise through failure and setbacks than through constant success; derived from a poem by Tang poet Liu Yuxi.

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Definitions
CC-CEDICT