Why Every PM Should Keep a Decision Journal

I've made thousands of product decisions. Most of them, I've forgotten. That's a problem.

If you can't remember what you decided and why, you can't learn from outcomes. You can't calibrate your intuition. You just keep making decisions based on vibes, while calling it "experience."

The decision journal system

Every week, I log 3-5 product decisions in a simple format:

Decision: What I chose to do Context: What I knew at the time Reasoning: Why I made this choice Confidence: How sure I was (1-10) Outcome: What actually happened (filled in later) Learning: What this taught me

What I've learned from 3 years of decision logging

1. My confidence calibration was terrible. Decisions I rated 9/10 confidence would sometimes fail badly. Decisions I rated 5/10 would succeed. Now my 8/10 actually means 80% hit rate.

2. Pattern recognition emerges. After 100+ logged decisions, themes appear. I started noticing: "Every time I prioritize without talking to customers first, I'm wrong." That became a rule.

3. I caught my own biases. I discovered I consistently overvalued engineering complexity and undervalued sales feedback. Seeing it in writing helped me correct.

4. It creates accountability. When you know you'll have to explain your reasoning later, you think harder upfront. The journal makes you a more rigorous thinker.

Practical tips

• Don't log every decision. Focus on ones with uncertainty or significant impact.
• Review monthly. Block 30 minutes to look at outcomes and update learnings.
• Be honest. No one reads this but you. Write the real reasoning, not the PR version.
• Keep it simple. A spreadsheet works. Don't over-engineer it.

Three years in, this is the single practice that's most improved my product intuition. It's free, takes 15 minutes a week, and compounds over time.