take the gilt off the gingerbread

Etymology
In the Middle Ages, gingerbread cakes were decorated with a thin layer of gold leaf. Without this casing, they were considered to be humble offerings, generally being little more than flavoured but stale bread.

Verb

 * 1)  To take away the most attractive or appealing qualities of something; to destroy an illusion.

Translations

 * Finnish: tehdä vähemmän houkutteleva, romuttaa kuvitelmat