《菜根谭·概论》
遇到表情阴沉、沉默寡言的人，千万不要对他推心置腹表露内心；遇到满脸怒气自以为是的人，在他面前就要小心提防不多说话。
遇沉沉不语之士，且莫输心；见悻悻自好之人，应须防口。
When you meet someone with a sullen expression and few words, don't open your heart to him; when you meet someone who is full of anger and self-righteous, be careful in front of him and don't talk too much.