Seneca wrote these words around 65 AD, in one of his final letters to Lucilius, while Nero was tightening the noose that would soon force his suicide. He was not theorizing. He was watching his own mind manufacture catastrophes, most of which would never arrive.

The line gets flattened on social media into a motivational bumper sticker, but the Stoic insight underneath is sharper. Seneca is not saying that pain isn't real. He is saying that the rehearsal of pain, the mental looping of worst-case scenarios, the 3 AM disaster cinema our brains screen for free, costs us more than the events themselves ever will. When the real thing comes, you face it once. In imagination, you face it a thousand times.

Cats, notably, do not do this. A cat startled by a vacuum cleaner is fully stressed for ninety seconds, then returns to the loaf position with no residue. We are the species that turns a single awkward email into a three-day weather system. Seneca's prescription, borrowed by every modern CBT manual: name the imagined disaster, check if it has landed, come back to the present paw. The cat already knew.