I think you're mixing up concepts.
Sure there are people that make a living from marketing self-help. Some of them might even really enjoy it.
But flow as defined in the book "Flow: The Psychology of Optimal Experience" by Mihály Csíkszentmihályi[0], is "a state of concentration or complete absorption with the activity at hand and the situation." In the book, it gives a few guide rails. Just enjoying something is different from it being in the sweet spot of challenging you, triggering growth, enabling you to learn something new or achieve something.
Of course that could come from selling your book or making a YouTube video, but instead of focusing on other people, and their motivations, and what they get out of whatever they're doing, the whole point is to figure out where you are really in a flow state that you personally find fulfilling, and would want to repeat. If you can't find that, then forget about, ignore all the information out there, and find a different life goal to pursue.
[0] https://www.goodreads.com/book/show/66354.Flow