Really interesting to read everyones thoughts. My observations.. almost every rider ( not every but most) worries about being to heavy handed. I don't think I even always realize when I've become heavy handed but my description of a light hand would begin with a consistently relaxed lower back. I really agree that the lightness in my hand happens when the fluidness is in my seat. If my seat is following then the lightness, the independance can float through my rein no matter the length of rein, but the minute my lower back braces up, the wrong muscles get started or involved that's the minute I jump to my hands to save the moment. I actually think that's ok.. it's just the process of learning how to ride.
I agree- it is awesome if the lower back relaxes and everything become as light as a breath. It is also true that a light moment is a blessing and not a given. It is an experience, not a constant: what inspires us to achieve true lightness, not only in the hands, but in riding the horse: total trust and commitment towards each other.