A lot of organizations kid themselves that project success or failure rests solely in the hands of the project managers. In reality organizations that do projects consistently well have a high level of competency at several levels.
First, executives know how to initiate projects and set a clear strategic framework within which project managers and team members operate. Lack of this framework is the major source of scope creep and it comes from executives who don't know how to play their role.
Second, senior management needs to set priorities and allocate people's time based on those priorities. When there are no priorities or allocation of resources we have chaos and 70 and 80% project failure rates.
Third, subject matter experts and managers need to know how to develop requirements, not in terms of wish lists but in terms of the business value that is needed.
Only when this foundation is in place can project managers and team members achieve consistent project success. Does your organization have all these pieces?