What is bad luck? Opinion. What are conflict, dispute, blame, accusation, irreverence, and frivolity? they are all opinions, and more than that, they are opinions that lie outside of our own reasoned choice, presented as if they were good or evil. Let a person shift their opinions only to what belongs in the field of their own choice, and I guarantee that person will have peace of mind, whatever is happening around them.
—Epictetus, Discourses, 3.3.18b-19 (resource), Ryan Holiday, The Daily Stoic