A good decision can turn out badly and a bad one can turn out well. If you judge decisions only by outcomes, you’ll learn the wrong lessons from both, and you’ll learn them confidently.

Process over outcome

Annie Duke, a former professional poker player, built Thinking in Bets (2018) on this idea. Her summary: “The quality of our lives is the sum of decision quality plus luck” Reported. You control the first term. The second arrives on its own schedule.

Without a record, everything gets filed by outcome, and the top-right and bottom-left boxes disappear. The dumb-luck box is where overconfident habits come from.

Judge the decision on what you knew and how you decided, not on how it turned out.

What to write

One entry per decision that matters: a launch, a big buy, a hire, a channel, a price change. Written before the result, dated, short.

• The decision and the options you considered, including doing nothing.
• What you expect, as a number with a range: “first-90-day revenue $150,000 to $250,000, most likely $180,000.”
• How confident you are, as a percentage.
• Why: the two or three reasons that decided it, and the base rate you started from.
• What would change your mind: the kill criteria, or the signal that would reopen it.
• A review date.

The review

Once a quarter, read the entries whose review dates have passed. For each, put it in a box of the table above. Then look across them. Are your ranges too narrow? If fewer than about eight in ten results fell inside ranges you called 80% likely, they are. Do you overrate one kind of reason? Which calls turned out right for reasons you didn’t write down? That’s where the learning is, and it’s invisible without the page.

Do this

• Start the journal today with the template in Appendix B, and write entries for the two biggest decisions currently open. Put the first quarterly review on the calendar.