Theres is three stages of learning. First is cognitive in which u see what needs to be done and peice it toghether slowly which can take anywhere from hours and days. The second stage is the associative stage in which you think about playing and constently use FEEDBACK to correctmistakes and this can overall take months to years. The its the autonomic phase in which you have become highly skilled and dont have to think about what you are doing....an example of this is walking. You dont think about walking, u just recall from your long term memory and follow with the procedure. This is what happens with professional, it is as easy as walking is to us. The upside of this is that as a person u can only have a certain amount of stimulus processed at once. Automation allows u to chunk stimulus togher by recalling through your long term memory. example is this, an illeterat see "t h e" as three letters, while a literate person sees it as "the" which is one-third the time in processing. The end result is you have much more time to do what you wish like sing or run around or notice people in the crowd while playing the guitar. Now that said when you begin to think about your actions you revert from autonomious (if you have reached this stage) back to cognitive taking much more time and more chances for mistake. A great example of this would be to ask your buddy next time if he breaths in or out during a golf swing...then he begins to think about it takeing away from his ohter aspects of performance and thus making a worst shot. Keep in mind i have taking half year courses on this material so this response does not do any justice however your are 100% right chacron, but the trick is u must be in the autonomous stage before you can do multiple task or atleast multiple task efficently.