《韩非子·说林下》
吴王派我们来的时候，本来就等着将军发怒呐！将军发怒了，吴军将深沟高垒；将军不发怒呢，吴军将麻痹懈怠。
吴使臣来也，固视将军怒，将军怒，将深沟高垒；将军不怒，将懈怠。
When King Wu sent us here, he expected General to become angry.  If the general becomes angry,  the Wu army will dig deep moats and erect high ramparts; if the general does not become enraged, the Wu army will relax and become lazy.