"Adversity has the effect of extracting talents that, in prosperity, would have remained dormant."
Source not yet traced to a specific passage, so treat the exact wording as unverified. See disputed and misattributed quotes.
Not a Stoic. Horace is classed as Greco-Roman & Adjacent: Classical figures who shaped or argued with Stoicism — Socrates, Aristotle, Heraclitus, Cicero and others. Related, but not Stoic.