Reference for Berakhot 119:10

היכי דמי כגון דאשכח מציאה אף על גב דרעה היא לדידיה דאי שמע בה מלכא שקיל לה מיניה השתא מיהא טובה היא:

How can we understand this? — If for instance he found something valuable. Although this may [eventually] be bad for him, because if the king hears of it he will take it from him, nevertheless for the time being it is good. IF A MAN'S WIFE IS PREGNANT AND HE SAYS, MAY [GOD] GRANT THAT MY WIFE BEAR etc. THIS IS A VAIN PRAYER.

Jastrow