

15-20 years ago I lived on about subsistence minimum for about 5 years.
No subscriptions. No TV. No car. No kids. Cook myself only cheapest food, no tobacco, no alcohol, no candy. Most of my furniture was used. Moved to a cheap-ish part of the country.
A piece of paper and guesswork to begin with many years ago.
My bank app has an automated thing that guesses (i can correct it but it’s right 90%) what every non cash transaction is and puts it in a category.
I can go back and look through how much things have cost me month by month.