Trust, but not too much.
More German Proverbs:
No one is wise enough to advice himself.German
Don't throw away your dirty water till you have got clean.
German
Much money, much friends.
German
One may see through a wall, if there's a hole in it.
German
That usury is a sin some hold, but take for granted they've no gold.
German
The sun will bring to light what lay under the snow.
German