Even a very clever person can make a silly mistake or be momentarily confused; everyone is fallible at times.
他向来精明能干，没想到这次也会犯这种低级错误，真是聪明一世，懵懂一时啊。
He has always been shrewd and capable, but I didn't expect him to make such a basic mistake this time; truly, wise for a lifetime, muddled for a moment.
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