Practice before the decision costs you.

Mental models are compact ways of seeing how the world works — thinking tools like inversion (solve problems backwards), incentives (behavior follows rewards), and second-order thinking (trace the consequences of the consequences). The right model makes a confusing decision suddenly legible.

Reading builds recognition; it doesn't build the reflex. Too Hard Pile is deliberate practice: short drills on realistic scenarios where you commit to an answer before anything is revealed, then spaced repetition brings each drill back until the model fires on its own mid-decision.

Yes — the free plan includes starter drills in two models, five decision journal entries, and the complete Decision Toolbox, with no time limit. The Trailblazer plan ($39.99/year or $4.99/month, plus taxes) unlocks all 13 models and 1,300 drills. You can try a drill with no signup at all.

About five minutes. A session is ten short drills; spaced repetition decides which ones you see, so time goes to the models you're still fuzzy on rather than the ones you've mastered.

Thirteen modules: four levels of inversion, first principles, second-order thinking, root cause analysis, incentives, premortem, risk and margin of safety, opportunity cost and trade-offs, deciding under uncertainty, and seeing the complete picture.

Exactly — and thinking is the one skill sitting upstream of everything else. Your job, your money, your relationships, your health are mostly the sum of thousands of decisions, and nearly all of them get made in seconds, with whatever thinking happens to show up. You don't get to skip those decisions; you only get to choose how well-equipped you arrive. Raise the average quality of your calls even slightly and it compounds the way money does — quietly, then unmistakably. One avoided bad hire, one caught sunk cost, one un-signed terrible lease. Those are the calls this trains you for. As Charlie Munger put it: "Spend each day trying to be a little wiser than you were when you woke up." That's the whole pitch. That's the whole product.

Honestly? Around week two, a little — and that's the design working. The moment a drill starts to feel repetitive is the moment your brain has stopped needing to struggle with it, which is exactly what "second nature" means. Psychologists call the urge to quit right there the motivational dip. Everyone who's ever learned an instrument calls it Tuesday. Sit through a few "boring" reps and one day the model fires mid-decision, on its own, without being asked — and that part never gets boring.

On the two most boring findings in learning science — chosen on purpose. One: memory fades on a predictable curve (Ebbinghaus mapped it in 1885), so each drill comes back right before you'd forget it. That's spaced repetition. Two: skills become automatic through repeated, effortful retrieval — "neurons that fire together wire together," as Hebb's rule is summarized. Bruce Lee put it more bluntly: "I fear not the man who has practiced 10,000 kicks once, but I fear the man who has practiced one kick 10,000 times." Or as Will Durant wrote, summing up Aristotle: "We are what we repeatedly do. Excellence, then, is not an act, but a habit." We didn't invent any of this — we just applied it to thinking.