小丑的悲哀只有面具能懂
[xiăo chŏu de bēi āi zhĭ yŏu miàn jù néng dŏng]
Translates to 'Only the mask understands the clown's sadness.' Implies the hidden sorrow or struggles that one tries to conceal beneath a cheerful or indifferent exterior, similar to the metaphor of a clown wearing makeup hiding real emotions.