The chief task in life is simply this: to identify and separate matters so that I can say clearly to myself which are externals not under my control, and which have to do with the choices I actually control. Where then do I look for good and evil? Not to uncontrollable externals, but within myself to the choices that are my own...
-- Epictetus, Discourses, 2.4.4-5
* Source: The Daily Stoic by Ryan Holiday and Stephen Hanselman