熟悉你的人刀子捅哪最痛
[shú xī nĭ de rén dāo zi tŏng nă zuì tòng]
This saying 'One who Knows You Best Can Find Exactly Where It Hurts Most With Even a Stab' illustrates the idea that those closest to you know your most vulnerable spots—emotionally, personally. In other words, friends, family or lovers can have more profound impacts on us, for better or worse.