What Does It Mean, To Be Mindful?

I've often heard about the usefulness of  meditation and being mindful, even in connection with controlling ADD.  I wonder about that.  It seems my mind is full enough! 

They (whoever 'they' are) talk about information overload, and I think that is one of my biggest problems.  It probably is the root cause of my insomnia, too.  My mind is so full of information of all kinds, from trivia to vital, life-changing ideas, it has so much indigestion, it can't settle down and let me sleep.  So, I lie awake, staring at the ceiling, or I doze off, only to have my eyes pop open to stare at the ceiling some more.  What is so interesting about the ceiling in the dark?  I can't see anything up there, but still my eyes pop open and stare at it.

If mindfulness means to be aware of what's going on in my mind, that's bound to keep me awake.  If the trick is really to empty the mind, then isn't that really mindlessness, and isn't that akin to insanity, as in I've lost my mind?  Or, is an empty mind the same as an empty head?  Either way, I'm in trouble.