The Enchiridion by Epictetus, a classic text of Stoicism, starts with this fundamental idea:

“Some things are under our control, while others are not under our control. Under our control are conception, choice, desire, aversion, and, in a word, everything that is our own doing; not under our control are our body, our property, reputation, office, and, in a word, everything that is not our own doing. Furthermore, the things under our control are by nature free, unhindered, and unimpeded; while the things not under our control are weak, servile, subject to hindrance, and not our own.”

The key to happiness and inner peace is simple. No matter what happens in your life. And that’s not an understatement. No matter what happens, always remember to focus on what’s within your control. I can pretty much guarantee that every time you were overwhelmed, it was because you ignored this first rule of Stoicism.