For if a person shifts their caution to their own reasoned choices and the acts of those choices, they will at the same time gain the will to avoid, but if they shift their caution away from their own reasoned choices to things not under their control, seeking to avoid what is controlled by others, they will then be agitated, fearful, and unstable.

—Epictetus, Discourses, 2.1.12, (resource), Ryan Holiday, The Daily Stoic: 366 Meditations on Wisdom Perseverance and Art of Living