I think you are describing "how to learn effectively, manage time, and stay motivated [once you've picked a topic]" - which is important and useful, but IMO slightly different from what the OP is describing (and a problem I have), which is "how to pick what to learn next when there are 1,000 interesting choices with uncertain payoffs"

For example, you say "Learn one thing at a time" - Sure, but how do you pick that one thing when there are 1,000 things on your list that all seem equally useful and interesting? What I am looking for is a proper system for picking that one thing, not using my gut feeling.