I use vimwiki to journal throughout my day. It's basically a stream of thoughts, to put structure in my workday. It's kinda like a dumbed-down version of Zettelkasten if you've heard of it. Or maybe you've heard of Obsidian. That one adds nice visuals to this idea of a second-brain on paper.

To answer your question, very useful. If only for yourself. Unless you're like a genius, not many people will be interested in reading your every little thought.