My first thought is always of light.
When the light is right and everything is working for me, I feel as tense as when making a difficult maneuver high on a mountain. A minute - and sometimes mere seconds - can make the difference between a superb image and a mundane one.
When the magic hour arrives, my thoughts center on light rather than on the landscape. I search for perfect light, then hunt for something earthbound to match with it.
I find it some of the hardest photography and the most challenging photography I've ever done. It's a real challenge to work with the natural features and the natural light.