Decision journaling: how to record why you decided something
A decision journal is a short written record of your reasoning at the moment you decide — made before you know how it turned out. It exists for one reason: your memory of why you decided something is rewritten by the outcome, automatically and without your permission. If it worked, you remember being confident. If it failed, you remember having doubts. Neither memory is reliable, and both actively prevent you from learning.
The problem it solves
Two well-documented effects make unaided decision review nearly worthless.
Hindsight bias means that once you know the result, you cannot recover how uncertain you were. The past reorganises itself into a story where the outcome was foreseeable. This feels like insight and is the opposite of it.
Outcome bias means you judge the quality of a decision by the quality of its result. But in any domain with real uncertainty, good decisions sometimes lose and bad decisions sometimes win. If you only learn from outcomes, you will learn superstitions: you will drop a sound process because it failed once, and keep a reckless one because it paid off.
A written record made before the outcome breaks both. It is the only cheap tool that does.
The minimum viable format
Five fields. If it takes longer than four minutes, you will stop doing it, and a journal you stopped is worth nothing.
1. The decision, in one sentence
What you are choosing, and what you are choosing against. Naming the rejected option matters — most of the information is in what you turned down.
2. What I expect to happen
A concrete prediction with a rough confidence and a date. "I think we ship by the 20th, maybe 60%." Vague expectations cannot be wrong, and a prediction that cannot be wrong teaches you nothing when you reread it.
3. Why — the actual reason
Not the presentable reason. If the honest driver is "I am tired of this argument and want it over," write that. The journal's entire value is in being more candid than the version you would tell a colleague. A sanitised journal is a second layer of self-deception with extra steps.
4. What would change my mind
Name the evidence that would make this wrong. This does two jobs: it forces you to notice whether such evidence exists at all, and it gives your future self a tripwire. Decisions without a stated falsifier are usually conclusions you had already reached before you started reasoning.
5. State
One line: rushed, tired, angry, excited, under someone's pressure. After thirty entries this is the field that pays. Almost everyone finds a state that reliably precedes their worst calls, and that pattern is invisible from inside any single decision.
Which decisions to journal
Not all of them. Journal a decision if it meets any of these:
- It is hard to reverse — a job, a move, a hire, a large purchase, ending a relationship.
- You are genuinely uncertain — if you know the answer, there is nothing to learn.
- It is a recurring type — the same shape of call you make monthly. These give you a sample size fastest.
- You feel unusual urgency to decide right now. That feeling is itself worth a record.
Five to ten entries a month is plenty. Journaling everything is the fastest way to journal nothing.
When and how to reread
The journal only pays on reread, and this is the step people skip. Two passes:
Outcome pass. When a decision resolves, open the entry before you write anything, and read your prediction first. The gap between what you wrote and what you now remember writing is the lesson — usually a bigger lesson than the outcome itself.
Pattern pass. Every quarter, read the last three months in one sitting and look only for repeats: recurring states, recurring blind spots, a category of decision you consistently rush. Individual entries are anecdotes; thirty entries are data.
Traps
- Writing for an audience. The moment you imagine someone reading it, you start justifying instead of recording. Keep it private and keep it ugly.
- Backfilling after the fact. An entry written after you know the result is not a journal entry; it is a memoir, and it is contaminated. If you missed the moment, skip it.
- Only journaling the big ones. Large decisions are rare, so they never accumulate into a pattern. The recurring medium-sized calls are where the learning actually is.
- Grading yourself. The point is calibration, not a score. Ask "was my reasoning sound given what I knew," and answer that question separately from whether it worked.