The Stoics recommended imagining the worst thing that could happen to you
It sounds like the opposite of positive thinking, and that's precisely why it worked.
There's a reliable trick your brain plays on you: whatever you have, you eventually stop noticing. Psychologists call it hedonic adaptation — the new house, the new relationship, the raise, all of it fades into background noise within months. The Stoics had a countermeasure two thousand years before anyone ran a lab study on it.
They called it premeditatio malorum, a few minutes, a few times a week, spent deliberately imagining the loss of something you value. Not dwelling on it, not spiraling. Just a clear-eyed look at the fact that your job, your health, the people you love, could be gone by evening. Marcus Aurelius practiced a version of it every morning. Seneca wrote entire letters urging a friend to rehearse loss so its arrival would never be a total shock.
The philosopher William B. Irvine, reviving the practice for modern readers, called it the single most useful tool in the whole Stoic kit. Not because it prepares you for catastrophe — grief still arrives as grief — but because it interrupts the numbness. You come back from ten minutes of imagined loss and the actual, ordinary, still-intact life in front of you looks briefly astonishing.
Gratitude, it turns out, sometimes needs a rehearsal of its opposite.