For the last 5 years or so I've been keeping daily journals, which have migrated from one piece of software to another over time. Ultimately they all boil down to Markdown files named `YYYY/MM/DD.md`, the format has evolved into me just throwing a timestamp in as a header and then typing whatever thoughts I have.

These are useful for a couple of purposes, the first is simply getting thoughts out of my head and into a document. The other thing they've been good for is tracing back through what I've been doing - my job involves a lot of context switching, and it can be good (and sometimes also useful) to be able to scroll back through the last month and be reminded that I have in fact achieved something.