Story is about an internal struggle, not an external one. It’s about what the protagonist has to learn, to overcome, to deal with internally in order to solve the problem that the external plot poses. That means that the internal problem predates the events in the plot, often by decades. So if you don’t know, specifically, what your protagonist wants, what internal misbelief is standing in his way—and most important, why—how on earth can you construct a plot that will force him to deal with it? The answer is simple: you can’t.
