The envelope of old receipts can contain a household’s forgotten priorities.

Spending records what people actually decided, as opposed to what they meant to decide. An envelope of old slips shows the winter the boiler went, the year of the piano lessons, the month somebody kept buying flowers. None of it was written down as a priority, and all of it was one.

If you come across a bundle like that, read a few before throwing them out. Then look at last month’s own spending with the same eye, not to judge it but to see it. What you paid for is a fairly accurate description of what mattered at the time.