No accidents are so unlucky ...

No accidents are so unlucky [bad] but that the wise may draw some advantage [good] from them.
No accidents are so unlucky [bad] but that the wise may draw some advantage [good] from them.

More phrases

If one does not know to which port one is sailing, no wind is favorable.
What a distressing contrast there is between the radiant intelligence of the child and the feeble mentality of the average adult.
We are masters of the unsaid words, but slaves of those we let slip out.
I have always found that mercy bears richer fruits than strict justice.
A lie gets halfway around the world before the truth has a chance to get its pants on.

Quotes from the same author

A true friend is the greatest of all blessings, and that which we take the least care of all to acquire.
In friendship as well as love, ignorance very often contributes more to our happiness than knowledge.
A true friend is the most precious of all possessions and the one we take the least thought about acquiring.
He is a truly virtuous man who wishes always to be open to the observation of honest men.
There are no events so disastrous that adroit men do not draw some advantage from them, nor any so fortunate that the imprudent cannot turn to their own prejudice.