Vigneshwar’s blog

How to Keep a Lessons Learnt Log

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One table. One review cadence. Compounding professional judgement.

1. The table

One row per lesson. Keep it in a single sheet or note. Never split by project.

# Date Context Trigger Plus Minus Next Tag Reviews Status
14 Aug 12 Vendor onboarding, Line 2 Missed SOP date by 3 wks Early risk flag to CEO Accepted verbal commitment, no written date Every vendor date in writing, same day Vendors 1 Open
15 Aug 19 Weekly review 3rd late-start meeting this month — Agenda sent <1 hr before Agenda 24 hrs prior or meeting cancelled Meetings 2 Principle

Column rules

  • Context: where it happened. Five words.
  • Trigger: the event that made you notice. Specific, not abstract.
  • Plus / Minus / Next: what worked, what didn't, what changes. Next must be an action you control.
  • Tag: one category (People, Vendors, Meetings, Decisions, Estimates, Comms). Patterns show up by tag.
  • Reviews: count of times you've re-read this row and it still held.
  • Status: Open → Principle (survived 3+ reviews) → Retired (turned out situational or wrong).

2. When to write

Cadence Time What goes in
Daily 30 sec One row only if something actually happened. Blank days are fine.
Weekly (Fri) 15 min Read the week's rows. Add one row for any pattern that repeated.
Critical juncture 1 hr Launch, failure, exit, role change. Write within 7 days. Add 3–5 rows.

3. How to review

Cadence Action
Monthly Read last 30 days. Increment Reviews on rows that still hold. Mark wrong ones Retired.
Quarterly Sort by Tag. The tag with the most Open rows is your current weakness. Pick one Next and make it a habit for the quarter.
Annually Filter Status = Principle. This is your professional operating manual. Carry it into the next role.

4. How to use it to get better

  1. Before a decision: filter by Tag. Read Principles. Takes 2 minutes, prevents repeat mistakes.
  2. Before a 1:1 or review: pull the last quarter's Minus column. This is your honest self-assessment, already written.
  3. Before an interview or role change: Principles column is your answer to "what have you learnt."
  4. When mentoring: hand over Principles by Tag. It's the only transferable part of experience.

5. Failure points

Failure Fix
Rows are vague ("communicate better") Rewrite Next as a rule with a number or deadline.
Log grows, never re-read Review cadence in calendar. No review, no compounding.
Only Minus rows Log the Plus. You need to know what to repeat, not just what to stop.
Split across projects One table. Patterns only appear across contexts.

Principle: Capture is cheap. Review is where the return comes from.