Often, project managers work with their heads down and focus on the original plan and steps rather than adapting to overcome challenges. If you know what success looks like, you won't risk wasting time on non-value added details. And most importantly, you'll be ready to adapt as the route changes.
Unsuccessful projects are characterized by rigorous attention to detailed planning. But the greater the detail, the more likely stakeholders will start disagreeing among themselves. The project is wasting its energy.