你非我怎知我心我非你怎知你心
[nĭ fēi wŏ zĕn zhī wŏ xīn wŏ fēi nĭ zĕn zhī nĭ xīn]
A reflection on mutual understanding or lack thereof. In simple words, you cannot truly understand another's mind unless you become them. Expresses the complexity and mystery behind human relationships and psychology.