When fortune knocks, open the door.
More German Proverbs:
The dog does not get bread every time he wags his tail.German
All good things must come to an end.
German
A lot will stick to dirty hands.
German
If the landlady is fair, the wine is fair.
German
So many countries, so many customs.
German
Those who don't pick roses in summer won't pick them in winter either.
German