It has taken me about five failed novels to really understand the truth of these words.
When I envisioned the stories of my earlier novels (all abandoned and deleted now), what I thought about was actually the plot--what happens, the events, and my job was to figure out ways for my characters to get where I wanted them to go and do those things I wanted them to do. The stories came out flat and prescribed and I didn't know why.
I was not actually thinking about story, the internal change of the characters by the events of the plot. But the plot actually develops and moves forward because the character wants something, faces opposition (conflict), acts to overcome those obstacles, then ultimately succeeds or fails.
This is the logic of story. The cause and effect of actions and inactions by and of our characters as they move toward achieving their goals. Sometimes that doesn't jive with those initial musings we have about the book we want to write. And that's OK because the story is ultimately about our characters and not our agenda.
Even if we think that agenda is super.