Not every difficult and dangerous thing is suitable for training, but only that which is conducive to success in achieving the object of our effort.

The saying cautions against confusing hardship with progress. Epictetus’s Stoic ethics emphasizes purposeful discipline: we should choose exercises (askēsis) that strengthen the capacities relevant to our aim—especially the governance of judgment, desire, and aversion—rather than courting danger or difficulty for its own sake. In other words, “tough” is not automatically “useful.” Training should be measured by whether it improves our ability to live well (in accordance with reason and virtue), not by how extreme it feels. The quote also implies a practical standard for self-improvement: evaluate practices by outcomes aligned with your objective, and avoid performative or reckless trials that inflate pride but do not cultivate character.