All the parts are Separate
All the parts are Connected
Successfully managing a project is a systems management process. Project's have parts that are separate - look at the Work Breakdown Structure.
Project's have parts that are connected - look at the Integrated Master Plan and Integrated Master Schedule.
Project's have combinations of separate and connected - look at the Integrated Risk Management processes.
Project Management has Principles, Practices, and Processes. If we don't see the whole and the parts at the same time, our chances of success are reduced.