Field notes · Idea · 3 min read · Reflect and learn

Turn a lesson into a rule you will use

You learned something the hard way. A meeting went badly because you skipped a step, or a launch went well because you did one particular thing. A month later you are in the same kind of situation and you have forgotten what you learned.

The idea

Atul Gawande's The Checklist Manifesto argues that experts fail less often from not knowing something than from not using what they already know. A short written checklist, he says, protects against that. His clearest example comes from surgery. In a study across eight hospitals, a 19-item surgical safety checklist was followed by a drop in inpatient complications from 11.0% to 7.0% and in deaths from 1.5% to 0.8%. Gawande was the senior author of that study, so the book and the evidence are not independent.

Ray Dalio's Principles shows a more personal version. He wrote down rules drawn from his own decisions and mistakes, and he revised them as he went. A separate line of research on reflection adds that stopping to think about what you have learned helps: in a Harvard Business School working paper, trainees who spent the last 15 minutes of each training day reflecting did better on the final test than those who did not.

What it gets right

Putting a lesson in writing turns a vague feeling into something you can reuse and correct. And the checklist research is a reminder that the point is not cleverness. It is making sure the thing you know actually happens at the right moment.

Where it breaks in a real week

The surgery study compared the same hospitals before and after, so other changes over time cannot be ruled out. A later study of 101 Ontario hospitals, after checklists were required, found the adjusted risk of death went from 0.71% to 0.65%, too small a change to count, and no clear drop in complications. Its authors suggest that how a checklist is introduced matters. Checklists also suit routine, repeatable steps. Most personal lessons are judgment: "when a design discussion gets abstract, bring two concrete examples" is a rule of thumb, not a checklist. And Dalio's principles are one person's account of one firm; there is no evidence they would help you. Writing too many rules is its own failure, because then none of them are used.

How Trellis builds it in

A Playbook entry is guidance you chose to keep. Trellis never creates one for you: an entry exists only after you confirm it, either directly or from a capture you reviewed. An entry holds the guidance, an optional "when to use" so you can recognize the moment, and a link back to the capture it came from. You can revise it, retire it or restore it, and its history keeps the earlier wording. A reflection stays a reflection until you decide it deserves reuse.

Trellis does not yet remind you of an entry at the right moment. You find it by looking in your Playbook. That is a real limit, and I would rather say so than imply the tool does the remembering.

Try this week

1. Pick one situation that keeps recurring, such as a kind of meeting or a kind of task.
2. Write one rule, one line on when to use it, and the experience behind it.
3. Use it next time, and note whether it helped. Revise it if it did not.

How strong is the evidence?

The surgical checklist result is a published study, and a larger later one did not find the same benefit. Gawande's and Dalio's books are practitioners' accounts, and the reflection result is a working paper. Together they support a modest claim: writing down lessons and returning to them can help when you use them, and you should test your own rules.