There's a lot of talk of the urgent vs. the important. 

And how to prioritize the important over the urgent. That's all good, yet people are largely unable to put this understanding to work all the time. And that's the issue with cool-sounding tenets with no fundamental reality attached to them - no one can truly internalize the concept, because they don't know why it's true, though they know it is, and it sounds like it is true. I'll attempt explaining the real reason why the important vs. urgent matters a lot. 

Most things - projects, goals, priorities - that fail, fail singularly due to one reason: Erosion. Or Corrosion. Call it what you will.

Important projects are like a living organism. They need constant love, care and attention, and boring maintenance - even when nothing is seemingly happening. Keeping an eye on progress, metrics and just overall health is the key ingredient, and a "Do Nothing" strategy because everything looks normal, is bound to lead to bad health eventually. 

The point is: Every time you prioritize the urgent over the important (at work, as in life), there's a little unseen erosion. The important stuff erodes little-by-little. Over time, you'll find yourself unsuccessful at having achieved anything substantive. And that's a risk none of us can afford.