> I have a hunch that most people who tend to read self-help books about habits work in such unstructured situations.

Yes. I do this and am self-employed. I developed a measurement spreadsheet for daily/weekly satisfaction and eventually figured out a good way to keep negative outcomes in check. A lot of it involves being very protective of my time and forcing balance into every day.

I also used to teach artists and the really high-end artists always laughed and said they were very organized, contrary to society's expectations of them.