Answer: One day at a time.
In 1975 Professor Fred Brooks wrote a book called the Mythical Man Month which was full of good ideas and observations on how to successfully blow a project schedule and budget out.
His basic observations were about the increase in complexity and the importance of communication as the number of people on the project increases. Eventualy you'll have so many people that the work becomes too complex.
Are his observations from 1975 on software project management still relevant in today's agile/ mega-project infatuated world? You be the judge.