I actually came across this saying many years ago, but from what exact source I don't remember.  It has served me well when I've remembered it, providing structure at the jumping-off point of an initiative.  A good example is the planning of collaborative Social Studies/English projects.  Before we start the project, I sit down with the English teacher, and we discuss our ultimate goals for the project before we create the calendar and schedule out activities.  In some instances I believe I can even take this habit too far.  I will set a goal for myself far into the future, and even though circumstances change that make achieving that goal less likely/reasonable, I will hold fast and suffer the consequences in pursuit of "the end" I originally envisioned.  To teach this concept, I plan on having students set a goal ("the end") for the end of the semester or year.  Then to keep that goal constantly "in mind," I will have them replace their cell phone wallpapers with an image that represents their chosen goal.  Since teenagers can't go five minutes without looking at their phones, my hope is that this strategy will constantly remind them of their chosen goal, and keep them more focused on the path to achieving it.