I realize that many people have believed and still do believe that the world is run by God and by fortune and that however shrewd men may be they can’t do anything about it and have no way of protecting themselves. As a result they may decide that it’s hardly worth making an effort and just leave events to chance… Sometimes, thinking it over, I have leaned a bit that way myself.
All the same, and so as not to give up on our free will, I reckon it may be true that luck decides the half of what we do, but it leaves the other half, more or less, to us. It’s like one of those raging rivers that sometimes rise and flood the plain, tearing down trees and buildings, dragging soil from one place and dumping it down in another. Everybody runs for safety, no one can resist the rush, there’s no way you can stop it. Still, the fact that a river is like this doesn’t prevent us from preparing for trouble when levels are low, building banks and dykes, so that when the water rises the next time it can be contained in a single channel and the rush of the river in flood is not so uncontrolled and destructive.
Fortune’s the same. It shows its power where no one has taken steps to contain it, flooding into places where it finds neither banks nor dykes that can hold it back.