有几种方式
first know others,then confend them
Know yourself, know your opponent;in a hundred battles, win a hundred victories.
Keep your friends close; keep your enemy
closer．
Know the enemy and know yourself, and you can fight a hundred battles with no danger of defeat.
出自英国汉学家翟林奈(Lionel Giles),1910年
In order to win,know thyself and thy enemy