The Decision Journal — Write Down Decisions So You Learn From Them
Tim Ferriss's decision-making tool: write your decision, your expected outcome, then review it 3 months later. Your judgment gets better every time you compare what you expected to what happened.
The idea
A decision journal is a simple record: when you make an important decision, you write it down. What are you deciding? What outcome do you expect? When? Then you date it. Three months later, you revisit it: did the outcome happen? Was your expectation right? If not, why not? What would you do differently? Over time, this calibrates your judgment. You stop trusting gut feelings and start trusting data about yourself — which decisions you make well, which you get wrong, what signals matter. Most people think their instincts get better with age. The truth: only if you have a feedback loop. The decision journal is that feedback loop.
Who is this for?
Vikram Tiwari
Engineering Manager · Hyderabad
Vikram's gut instincts: 3 hires underperformed, 2 rejected became stars elsewhere. His judgment? Not as good as he thought.
Decision journal: "Hiring Asha: 8 yrs, systems thinking, hesitant deep-dives. Expected 8/10." Six months: Asha solved his team's hardest problem.
Pattern: undervalued quiet engineers, overvalued charisma. Year one: hiring improved 30% — just by tracking, not working harder.
"I thought I was a great judge of people. The journal proved I was just OK. But once I saw the patterns, I could actually improve."
What you'll get
A decision journal with your first 5 decisions logged
Decision, expected outcome, date. Not overthinking it — just writing it down.
A feedback loop for your own judgment
Three months from now, you'll revisit this and see where you nailed it and where you were wrong.
Evidence of how your judgment actually works
Not your gut feeling about your gut feeling — real data about your decision accuracy over time.
A repeatable pattern for calibrating wisdom
Write, wait, review, learn. Repeat. Over a year, this transforms how you make decisions.
Watch
Tim Ferriss · strategy · ~6 min
Do the challenge
1Create your Decision Journal — one page or file
Open a Google Doc, Notion page, or any document. Title it "My Decision Journal." That's it. You'll use this for one decision a week, minimum.
2Pick one decision you made recently — this week
Don't wait for a "big" decision. Today: which project to prioritize? Which vendor to use? Whether to send that email or sleep on it? Write it down. What did you decide? What's the expected outcome?
3Make a calendar reminder to review in 3 months
Three months from today, revisit this decision. Did the outcome happen? Was your expectation right? If not, what signal did you miss? What would you do differently?
4Log one decision per week, building the journal
By the end of this week, you'll have 2–3 decisions logged. By month 2, you'll have 8. By month 3, you'll revisit your first decisions and see how accurate your judgment actually is.
Your template
DATE: Sept 4, 2026 DECISION: Switch the team to a 4-day work week (async Tuesday, sync Wed-Fri) EXPECTED OUTCOME: Same output, better focus, 15% higher satisfaction CONFIDENCE: 7/10 REVIEW DATE: Dec 4, 2026 --- DATE: Sept 2, 2026 DECISION: Reject the consulting offer; stay in-house EXPECTED OUTCOME: Slower short-term income, but stronger equity upside and learning CONFIDENCE: 8/10 REVIEW DATE: Dec 2, 2026
Knowledge Check
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