Earlier quoted context omitted.
How? Chronologically or structured by topics? Appending at the top or buttom? Timestamps? Tags? How do you navigate through the file?
There are a couple sections, but for the most part it's chronological, with new entries at the bottom. Started adding dates to new notes/quotes/observations about 5 years ago. It's a sprawling mess, so I rely on search to find what I'm after. I reference it often -- it's like an extension of my brain.
Similarly, several years ago I added a keybind to my .vimrc that, by typing ",a" I'm moved to the bottom of the file and today's date with a separator line underneath. My leader key is "," and I mnemonically associate "a" with "append".
The earliest date recorded in it goes back to 2006 and is about 300KB in size. I still reference and add to it on a regular basis.