The bullet journal community has developed genuinely useful systems and I want to be respectful of them, because the discipline they show is real. What I am about to describe is not one of those systems. It is the anti-system: what happens when you accept that you will never keep up an index or a monthly log, and you just write in the notebook chronologically until it is full.
The setup: one A5 hardcover notebook, one fountain pen, dot grid pages. Everything goes in the notebook. Meeting notes, book quotes, to-do lists, phone numbers, birthday-gift ideas, half-formed essays. Each page starts with the date and the location (kitchen table / airport / office). That is the entire organisational scheme.
What this trades off: retrieval. If I want to find something specific I wrote three months ago, I have to flip through the notebook. This is slower than any digital system. What I gain in exchange: I actually keep the notebook. The friction of maintaining an elaborate system is exactly what kills the habit for most people. My anti-system has zero friction. I have filled 14 notebooks this way in four years. They live on a shelf. About once a year I skim through the oldest one and delete pages I would never miss, and the useful ones migrate into a shorter reference notebook. That is the whole workflow.