You made a decision three months ago that turned out badly. Now you're trying to figure out whether it was a bad decision or just a bad outcome. You know the difference matters — good decisions can have bad outcomes due to bad luck, and bad decisions can have good outcomes despite poor reasoning. But you can't reconstruct your thinking from three months ago. You remember the outcome, which colors everything. You've already rationalized your reasoning to fit what happened.

This is the fundamental problem a decision journal solves. By documenting your thinking at the time of a decision — before you know the outcome — you create a record that can't be revised by hindsight. You can actually evaluate the quality of your reasoning, separate from the quality of the result.

Decision journals are a well-known tool among professional investors, military strategists, and cognitive psychologists. Most people who try one abandon it because the friction of maintaining a structured journal is too high. AI notes remove that friction. You capture your thinking naturally, and the journal builds itself.

What to Capture at Decision Time

When you face a significant decision, capture a quick note with four elements:

1. The decision itself — what you chose and what alternatives you considered

2. Your reasoning — why you chose this option over the alternatives

3. What you expect to happen — your prediction for the outcome

4. Your confidence level — how sure you are (very confident, somewhat confident, a coin flip)

This doesn't need to be elaborate. A Voice Mode capture works perfectly: "Decided to hire a contractor instead of a full-time employee for this project. Main reason: we're not sure the workload is permanent, and I don't want to commit to a salary before we validate demand. I expect we'll know within three months whether this becomes a full-time need. I'm about 70% confident this is the right call — the risk is that a contractor won't have the same investment in quality."

That's ninety seconds. The decision, the reasoning, the prediction, the confidence. All captured before the outcome is known.

Creating a Decision Collection

Create a collection for your decision journal. Every significant decision note goes in. Over months and years, this collection becomes one of the most valuable things in your notes — a map of how you think, decide, and learn.

"Significant" is subjective and personal. You might journal hiring decisions, investment decisions, strategic bets, career moves, relationship choices, health decisions, or big purchases. The common thread is: decisions where the outcome is uncertain and the stakes are high enough that learning from the experience is worthwhile.

The Outcome Review

The real value of a decision journal comes when you revisit decisions after outcomes are known. Set a reminder — or better, make it part of your regular review practice — to check back on past decisions.

Open Mem Chat:

"What decisions did I make three months ago? Summarize my reasoning and predictions."

Now compare your predictions to reality. Were you right? Were you right for the wrong reasons? Were you wrong? Were you overconfident?

The honest answers to these questions are extraordinarily useful. You might discover that you're consistently overconfident — you rate decisions as 90% likely to succeed, but they succeed only 60% of the time. You might find that you systematically underweight a specific type of risk. You might realize that your best decisions share a common pattern (thorough research, consultation with a specific person) and your worst decisions share another (time pressure, emotional investment).

For more on building a regular review practice, see our guide on the one-question weekly review.

Pattern Recognition Across Decisions

Individual decision reviews are helpful. Pattern recognition across many decisions is transformative. Ask Chat:

"What patterns do I see across the decisions I've made this year — the ones that went well and the ones that didn't?"

"When I've been overconfident in my decisions, what did those situations have in common?"

"What types of decisions do I tend to agonize over, and how have those decisions turned out?"

These meta-queries use your decision journal as training data for your own judgment. You're not just learning from individual outcomes — you're calibrating your decision-making process itself.

This is what professional investors do when they review their trading journals. It's what military officers do in after-action reviews. The practice works because it forces honest engagement with your own thinking patterns, free from the distortions of hindsight.

Decisions in Context

One advantage of keeping your decision journal alongside all your other notes is context. Decisions don't happen in isolation — they're influenced by your emotional state, your workload, your recent experiences, the advice you received.

When you review a decision, you can also ask:

"What was happening in my life around the time I made this decision, based on my other notes?"

Maybe the decision you regret was made during a period of burnout, when your notes show you were stretched across too many projects. Maybe the best decision you made this year was informed by a book you'd just finished reading. The surrounding context enriches your understanding of why you decided as you did.

Heads Up can also surface relevant context. When you're facing a new decision and Mem surfaces a similar past decision from your journal, the historical perspective becomes immediately actionable.

Shared Decision-Making

For decisions made with a partner, co-founder, or team, the decision journal serves an additional purpose: it creates a shared record of why a decision was made. When disagreements arise months later — "We should never have done X" — the journal provides an honest account of the reasoning and the context. It prevents revisionist history and supports productive accountability.

This is particularly valuable in business partnerships where strategic decisions compound. When co-founders can review their shared decision history, they can identify whose instincts tend to be right in which domains, and allocate decision-making authority accordingly.

For more on documenting decisions rather than just discussions, see our guide on documenting decisions, not discussions.

Lowering the Bar

The decision journal only works if you actually use it. The biggest risk is making it too formal, too structured, too time-consuming.

The minimum viable journal entry is a voice note: "I decided X because Y. I think Z will happen. I'm somewhat confident." That's fifteen seconds. Over time, you can add more depth to the entries that warrant it. But start with the habit, not the system.

AI notes make the review process effortless — that's the real unlock. Capturing decisions is simple. The hard part has always been going back and actually reviewing them. When Chat can synthesize your journal and surface patterns on demand, the review happens because it's easy, not because you're disciplined enough to re-read months of entries manually.

Get Started

1. The next time you face a significant decision, capture a voice note with your reasoning, prediction, and confidence level

2. Create a "Decisions" collection and tag your entries

3. In three months, ask Chat to summarize your recent decisions and compare predictions to outcomes

Try Mem free →