Friedrich (Wilhelm) Nietzsche, 1844-1900
was a German philosopher
Out of life's school of war: What does not destroy me, makes me stronger.
( “Twilight of the idols, or, How to philosophize with a hammer”, 1888 )
Whatever does not destroy me makes me stronger.
Karl Kraus, 1874-1936
was an Austrian author and journalist
A weak man has doubts before a decision, a strong man has them afterwards.