know the enemy and know yourself
英 美
As the Chinese saying goes, "know the enemy and know yourself, and you can fight a hundred battles with no danger of defeat", one should know both himself and his counterpart to win each battle.
中国有一名话:“知己知彼,百战不殆。”意思说,打仗的时候,既要了解自己,还要了解自己的对手,这样才能在每场战役中取胜。