When we learn to do anything new - how to drive, for example - we go through three stages. The first stage demands a lot of attention as we try out the controls, learn the rules of driving, and so on. In the second stage we beign to coordinate our knowledge, linking movements together and more fluidly combining our actions with our knowledge for the car, the situation, and the rules. In the third stage we drive the car with barely a thought. It's automatic. And with that our improvment at driving slows dramatically, eventually stopping completely.
By contrast, great performers never allow thmeselves to reach the automatic, arrested-development stage in their chosen field. That is the effect of continual deliberate practice - avoiding automacity. The essence of practice, which is constantly trying to do things one cannot do comfortably, makes automatic behavior impossible. It's certainly true that a great performer is able to do many things in his or her field with far fewer mental demands than a novice performer; an excellent pilot lands a 747 without breaking a sweat. But ultimately the performance is always conscious and controlled, not automatic.
Colvin's point is duly noted - life rarely remains stagnant - the environments we perform in rarely afford us the same situation over and over again. So we must remain adaptable, and to do that we must be very mindful and deliberately focused.
Think about your own driving skills. Unless you're Danica Patrick, you've probably entered a kind of automaticity stage with your driving. How much does your driving continue to improve while remaining in this automatic stage?
When we are no longer mindful and we do things with barely a thought, we sever ourselves from further gains and sabotage our potential in favor of a comfortable plateau.