Overthinking thoughts over thinking.

Have you ever tried to not think about anything? In the process, your thoughts are i'm not thinking anything. i'm not thinking anything. nothing is going through my mind. i won't think about anything. i won't write this down. and suddenly, your mind races through all the things you need to do, or if you let it go on creative auto pilot like i do, it starts thinking about story ideas, or blog ideas. it's virtually impossible for me to think about nothing, especially after such a long, thought-provoking day. for instance, i tried this today, and all i got was what happens when you let your brain go into auto pilot? have you ever wondered this? i'm almost scared to let it lead; to see where it takes me. hmm. i should blog about this. yep, i really want to blog about this. where are you if you're not thinking about anything? are you conscious? are you sleeping? but even in your sleep, you think-- in your dreams. do people in comas think? are they just not aware of their thoughts? is it truly possible to not think? do people in yoga classes accomplish this? how do you stop not thinking? is it a conscious decision to make thoughts again? are you able to immediately regain thought processes, or does it take a few seconds to get back into the swing of things? 
obviously, i'm not a pro yoga candidate. my head is full, even when it's empty. which makes for a difficult relaxing afternoon after labs, classes and work. i wonder how big my head will get this semester. because it sure hurts like it's growing, with all the thinking i'm constantly doing. :)