In almost every book, the protagonist learns some sort of skill that helps them overcome their main conflict/defeat the antagonist (the villain). It can be a physical skill (like hand-to-hand combat) or something as simple as learning to overcome their fears. (Sometimes it's both). You'll want to make sure that the skill the protagonist develops throughout the story plays a role in defeating the antagonist. If the skill doesn't have anything to do with the downfall of the antagonist, then the entire beginning/middle of your book will seem disconnected from the resolution.