The dichotomy of control
Epictetus, in the opening line of the Enchiridion, divides the world into two: what is up to us, and what is not. The first contains our judgements, our intentions, our use of attention. The second contains everything else.
The Stoic claim is not that the outer ring doesn't matter. It clearly does. The claim is that locating your peace there is a category error — like trying to keep a candle alight in the wind by demanding the wind stop. Move the dial below to choose where you place the centre of gravity of your peace. Watch the marker change.