een bord voor je kop hebben

Etymology
Literal translation: “to have a sign/plate in front of your head”. The origins are uncertain, but the saying already occurred at the beginning of the 17th century.

Verb

 * 1)  to do as one pleases without shame or regard for signals from others
 * 2)  to be blissfully ignorant
 * 1)  to be blissfully ignorant