Summary
Seneca reminds us that the strength of a rational soul is far superior to any external fortune, whether good or bad. Unlike luck, which is unpredictable and fleeting, the rational soul has the power to guide its own life and make decisions that lead to happiness or misery. This inner strength allows a person to navigate life’s ups and downs with stability and wisdom, rather than being at the mercy of external circumstances.

Interpretation
In practical terms, this means that a wise person doesn’t rely on luck for their happiness but instead focuses on cultivating their inner strength and rationality. For someone familiar with Stoic teachings, this emphasizes the importance of self-mastery and personal responsibility. True contentment comes not from external fortune but from how we respond to life’s challenges. By developing a strong, rational soul, we gain control over our own happiness, regardless of the circumstances we face.