I'm not sure if we are argueing semantics or touching on something significant here.
There are several issues here. I'm sure Van will have his say so when he gets a chance. We are fairly close (but not exactly the same) in our thoughts on this matter.
1) The ability to do a moderately (not highly) complex task in a manner that seems simple to you because the synaptic pathways are so well structured. If you never walked up a flight of stairs, it would seem like a complex task, and would require lots of conscious thought. You could never do it under stress. But because we all have done it perhaps thousands or tens of thousands of times, it could be done even under the highest stress level.
2) The actual mindset that one should "attempt" to achieve under a highly charged situation. Yes, I've heard all the stuff about chatacholamine cocktails and other extreme physiologic states. But the fact is that some of us perform better under stress than others; it is not an absolute. Training is certainly a factor, as is the genetic tendencies for mental disposition under stress.
By the way, there is a quote in the Tao of Jeet Kune Do that is worth mentioning. Something about not being tense but ready, not thinking but not dreaming, etc, etc, It describes this Platonic ideal of a mindset better than any description I've seen. I'll post it when I can get my hands on the book.