zhī jǐ zhī bǐ , bǎi zhàn bù dài
know yourself and know your enemy, and you will never be defeated (idiom, from Sunzi's "The Art of War" 孫子兵法|孙子兵法[Sun1 zi3 Bing1 fa3])
知
zhī
to know
己
jǐ
self
彼
bǐ
that
,
,
百
bǎi
hundred
战
zhàn
to fight
不
bù
no; not so
殆
dài
(literary) dangerous; perilous