Epictetus taught that only two things are truly in your control: how you relate to your thoughts and what actions you take. Worry is just a mental event. You can either change your relationship to it or take concrete steps to fix what caused it. Everything else, accept and let go.
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I was doing a podcast yesterday and we got to think about the things that are within your control and without your control. And essentially, one of the Stoics, Epictetus, said there are only 2 things you can control: how you relate to your thoughts and your actions. Your thoughts are just that, right? And so whenever something comes up and you're worried about something or you're stressed about something, it's how you relate to it that matters, because it is just an idea in your head. It is just a thought. And then the next thing you can control is what are you actually going to do about it? Am I going to take steps to alleviate this idea, this thing that worries me, and do that if it's within my control? If it's beyond my control, the only thing you can do is decide it, accept it, and let it go.