Go rate yourself "A, B, C, D, F" in your core business or vocation functions. There's probably, like, 5-10 of them.
Now, ask yourself, "If our goal was to be #1 in the field -- the very best -- what would the ratings be?"
It's easy to give yourself a couple A's, mostly B's, and the occasional C.
But grading out at a "C" in one key area -- being average -- might just be fatal to being the best in the industry. A "C" when measured against the field is quite possibly an "F" when measured with really being the best.
If you were very strictly grade yourself, would you really come away with more than a single "A"?
And, wouldn't you really have a few areas that are critically deficient and holding you back?
Try this exercise. It's eye-opening. Most people benchmark against average, so something that seems "OK" could well be fatal if you'd like to break out of the commoditized pack and be known as best of the breed for what you do.