Personally, one of the most helpful things I learned was three-act structure. For my first four or so novels, I built the structure intuitively.

He had been someone before. That person had been the result of a lifetime of choices, good and bad. And like it or not, he was drawing closer to that identity now. Not the freedom of infinite variety, but the tyranny of a decision made, a path walked, a life lived. What if he didn't like the view

Stephen King is open about the fact that he continues to learn the craft, and if King hasn't got it figured out yet, what the hell hope have the rest of us got?

No matter how long you spend at creation, you're always a student.

I'm always geeking out about something.

I didn't want to just write a series - I wanted to write an epic, on story that spans three books, where decisions made in the first impact the last.

Once I came to really understand the mechanics of three-act structure, my life got a great deal easier. It doesn't tell you how to write your book, but it helps you understand why things aren't working, or what kind of beat needs to come next.