I would think that you would more have to think about the general type of move, which training has made automatic through practice, and then do it. It is instinctive in that you don't have to lumber mentally through the entire process. This is already programmed into, as combos can be as well. This way when I mean to block, I block, and when I want to kick, I kick. No extra steps are taken, as it is all done immediately and the most efficient way; as practiced. However, i can still change my plan, and my combinations at will. At least thats what my experience has been, although I am not a street fighter. I guess it also comes down to the style of the fighter. Some people do well with instinctive fighting, and doing whatever comes naturally. Some can plan out what will be effective and immediately do it. Most others are somewhere in between I would surmise.