A good day of work leaves the next person with fewer mysteries.

Work is usually judged by what got finished, which ignores the state it was left in. The next person, who may be you in three weeks, arrives to find either a clear situation or a set of puzzles: what was tried, where things stand, what is undecided. Solving those puzzles is expensive and invisible in anybody’s account of the day. A note costs five minutes and saves an hour.

Before you stop today, write down where you got to and what the next step is. Include the dead end you already explored. Address it to somebody who was not there.