Greatest tragedies produce the greatest intensifiers.
—Eric Barker, Barking Up the Wrong Tree: The Surprising Science behind why everything you know about success is (mostly) wrong
They thought you didn't have control over anything but you choices. And if you can't control something you shouldn't worry about it.
Here's that Epictetus guy again:
Some things are in our control and others not. Things in our control are opinion, pursuit, desire, aversion, and in a word, whatever are our own actions. Things not in our control are body, property, reputation, command, and in one word, whatever are not our own actions.
Remember that it's not only the desire for wealth and position that debases and subjugates us, but also the desire for peace, leisure, travel, and learning. It doesn't matter what the external thing is, the value we place on it subjugates us to another... where our heart is set, there our impediment lies.
— Epictetus, Discourses, 4.4.1-2; 15