「日防夜防，家賊難防」

(pos:語句)
yue:字面指就算由朝到晚守住屋企，由於對屋企人冇戒心，始終防唔到屋企入面嘅賊；引申成好難防備唔老實、不忠嘅自己人，例如#穿櫃桶底、#內鬼、#間諜 等。
eng:it is difficult to defend against a dishonest or treacherous insider, such as a hidden traitor and a spy; literally: one can defend night and day but it is hard to defend against a thief from one's own family