The key to success in any endeavor is measurement.
I mean that quite literally. Without a quantifiable sense of where you are vs. where you were, you can’t know (in any meaningful way) whether you’ve succeeded or not.
When it comes to digital marketing, this truism barely needs stating. No marketer in his or her right mind would walk into the CMO's office without a set of precise measures indicating the success (or failure!) of last month's new campaign.