He who makes a mouse of himself, will be eaten by the cats.
More German Proverbs:
No diadem can cure a headache.German
Every one is glad to see a knave caught in his own trap.
German
The executioner is a keen shaver.
German
The best is the enemy of the good.
German
Good luck, with good looking after!
German
Sudden trust brings sudden repentance.
German