Building castles in the air.
More German Proverbs:
The fault of another is a good teacher.German
The devil likes to souse what is already wet.
German
He who has once invited the devil into his house, will never be rid of him.
German
The nearer the church the farther from God.
German
Except for the night, we could never know the stars.
German
A lovelorn cook oversalts the porridge.
German