Is your product successful because you were lucky, or because you were methodical and intentional? Do you want to build a plan where you are dependent on good fortune, or do you want to make your own “luck?” Both approaches work, but only one makes sense as an intention. Slide 3 of your presentation to a venture capitalist should not say "And then we get lucky!"
You can read more about successful product management in the recent article by Scott Sehlhorst: http://www.executivebrief.com/article/successful-product-management-lucky-or-intentional/.