The "Enchiridion" and "Selections from the Discourses" are influential works by Epictetus, a prominent Stoic philosopher. The "Enchiridion," which translates to "manual," serves as a practical guide to Stoic ethics and presents key philosophical principles. It emphasizes the importance of distinguishing between what is within our control and what is not, urging readers to focus on their reactions and attitudes rather than external events. This foundational idea is central to achieving personal tranquility and resilience in the face of life's challenges.