Bullet Journal is a concept by Ryder Carroll that makes it relatively simple to organize our life on paper.
It's awesome for freelancers, bloggers, artists, lawyers, etc. that look for a versatile way to put several things down on paper. For example, thoughts, to do lists, diaries, goals and aspirations, sketches and drawings.
Each person adapts it themselves, and so it becomes unique.
As he says in the video "It's an analog system I developed to track the past, organize the present, and plan for the future."
A normal diary feels 'square' in comparison. And imposes upon you their methodology.
In the site Ryder Carroll describes that Bullet journal is designed to be "... an evolving, adaptable platform meant to be shared and self curated as you determine what works best for you."
I discovered about it some years ago and I've been using it since. It doesn't look as nice as most of the bloggers that post about it, at sometimes I stay some time without using it, but it's there when I need and I find it a very good concept.
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How to do it