The first step in developing a successful team is setting a goal. After committing to the goal, the team starts to work towards it. Without the team’s commitment, the goal will never be reached regardless of how skilled the team is or what processes you follow. Imagine if you were told to complete a set of tasks with a defined date and you had no say in the set of tasks allocated and the date of delivery, would you be as committed to the goal? I suspect not! Therefore, Agile SCRUM and other Agile methodologies encourage mutual decision making by the people involved. 
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In SCRUM, the team makes a consensus decision on the Sprint Backlog. This means that whatever they decide to build and deliver during the Agile Sprint is owned by the team. Hence, the team is responsible for the output of the Agile Sprint. This is an important psychological factor, which will enable the team to make every conceivable effort to meet their commitment. After all, there is pride at stake. An Agile project leverages this basic human trait.
As a Scrummaster or a Project Manager, you need to ensure that you have highly developed Agile project management soft skills.