A story is about a problem. Your protagonist is the one experiencing the problem. Why? Because you, the writer, has designed him for it. The bigger the problem is, the bigger the person has to be, to be capable of resolving it. That’s why only your protagonist can resolve your story-worthy problem. The beginning of your book explains who it is about. The middle of the book explains why it is about him, and not someone else. The ending reveals what he does to resolve the problem.
There are two kinds of problems, crisis and challenges. A crisis requires immediate attention and is a situation the protagonist did not choose. Challenges can become a crisis if they are left unattended for long periods of time. A challenge is a self-created problem the protagonist chose. Readers are most interested in seeing the protagonist deal with both.
What you do, is who you are. How your protagonist addresses the problem, shows the reader who he is. What you say you do, is who you think you are. In every situation, you must ask the protagonist why this moment is important to him. Where does it hurt him? Why does it hurt him? What will make the pain worse? What will make the pain stop?
As a writer it is your job to hurt your protagonist and then continue to hurt him more and more. In fact, you should hurt him in as many ways as possible. Because if he doesn’t get hurt, why should anyone care? When you hurt him, you reveal his emotional core.
His problems are huge and his solutions are like solving a chinese puzzle box. The more he achieves to solve, the more complicated the problems turns out to be. Solving part of the problem reveals hidden parts of the problem. Nothing is easy. The problem unravels into all its component problems.
The hero’s discovery of the nature of the problem must put him up against the biggest test of all, himself. The story accounts of how he started out like this and ended up like that. Transformation occurs within the protagonist because every alternative has been tried and failed, all other options are exhausted, the self surrenders and surprises itself by reinventing itself.