Man is his own greatest enemy!
人最大的敌人就是他自己！
这是一个简单的主系表结构，用 'greatest' 最高级形容词强调程度，感叹号增强了情感色彩。
"they should remember to exercise self-restraint this is a matter of character."
"Eventually, a day came when the boy no longer lost his patience or his temper."
"Do not let yourself be your own enemy"
"When facing temptation do not struggle against it"
"Our greatest mistake is revealing our worst personality to those closest to us."