The trick is, bringing that utterly ordinary, everyday kind of mind into the stress of combat/keiko.
or to use a real world example.
I work in a restaurant. At peak hours it gets pretty hairy in the kitchen, and when I'm on my part of the line alone I have to go to this state in order to handle all of the orders, time them correctly to the rest of he lines work as well as handle requests from the serving staff coming in and out all without loosing my focus on the things I am working on. I can't stop and look at or think about what comes next. If I do it throws off my whole rhythm.And of spomeone comes into my focus they are likely to take a bit of verbal Ukemi ,backed by a large dose of Ki.
I have to be able to take in a situation and react to it immediately without thought, and have it be correct and sometimes I have to avoid colliding with someone who comes into my space when they don't belong there. In this state I am aware of ,and reacting to, everything going on around me and yet thinking about nothing. Its really quite cool. My perception of time slows way down.
Someday I'll achieve that in the dojo. I have a feeling that when I finally get there I am going to really have fun with Randori.