An urgent letter reached Cato while he was in a military camp: his half-brother, Caepio, was gravely ill. Cato had spent his life idolizing Caepio as only a younger brother could. And even as he outstripped Caepio in achievement, in discipline, and in public profile, Cato held his brother dear.

The road to Thrace, where Caepio lay dying, was too difficult. The sea looked impossible: a heavy storm was pouring rain on the Aegean coast, and no ship in port was large enough to brave the crossing and the squall. At last, Cato persuaded the captain of a small, one-masted merchant boat to make the passage, past the island of Thasos and through the northern Aegean. In those conditions, even with the right vessel, shipwreck was no idle threat, and Cato knew it. Yet he arrived in good time, storm-tossed and soaking, but still whole. Caepio was already dead.

So the Stoic was taught to pray, taught to welcome fate in, taught to see evil in greedy attachment to the beloved, not in the death that takes him away. So Cato was taught. But at this moment, the moment for which his philosophy should have prepared him above all others, it was all smoke. Only the corpse was solid. He embraced it, sobbed over it, ordered the best incense and the best clothes burned with it on a high pyre, ordered a massive marble likeness of Caepio set up in the market of the provincial Thracian town in which he had never before set foot—lavishing on the dead the luxury he railed against for the living.

Cato gave himself to grief, this once, with the same fervor that had led him to preach the problem of grief, the need for independence from pain in all things. For the rest of his life, friends and enemies alike would remark that this was the moment when philosophy most abandoned Cato. Stoic practice—even for the most practiced, like Cato—isn’t always going to serve us. There are times when the mask will slip, when our resolve will fail, when our attachments will get the better of us. This moment in Cato’s life didn’t undermine a lifetime of training; he would, in his later years, be remembered for the moments when he modeled Stoicism, not the one time when it failed to help him.

What does that mean for us? To not judge ourselves too harshly. We can set an ideal; we can practice virtue; we can steer ourselves in the stoic direction. But veering off course is bound to happen, even to the best of us. The important thing—for Cato, as for us—is how quickly we get back on course. How quickly our training comes to our aid in the next test of our reason against our emotions.