The teacher of my Project Management class, Mike Taylor, mentioned “Gresham’s Law of Planning” in last night’s class and told us to look it up. It turns out that the original Gresham’s Law was actually penned by economist Thomas Gresham and had everything to do with economics and nothing to do with planning – in short, it said “bad money drives out good money”. Later, some folks interested in project planning and time management saw an analogous principle with regards to time management and decided to call it Gresham’s Law of Planning. The best description of it that I could find with a quick web search came from here and it said:

An important principle of Organisation design that relates to managerial decision making is Gresham’s Law of Planning. This law states that there is a general tendency for programmed activities to overshadow non-programmed activities. Hence, if a series of decisions are to be made, those that are more routine and repetitive will tend to be made before the ones that are unique and require considerable thought. This happens presumably because you attempt to clear the desk so that you can get down to the really serious decisions. Unfortunately, the desks very often never get cleared.

In other words, you never get done the things you most want to get done, because life is a never-ending stream of interruptions.