Proprioception is your body's ability to sense its movement and position in space.
The lost sixth sense. Imagine running blindfolded. Or with numb feet.

Most of your sensory information during a run comes from proprioception. 
Your visual and auditory senses will help you guide your run, but 70% of what you need to know (where to land, how much force to use, when to push forward, etc.) comes from your feet. Seventy percent.

That is why what is on your feet is so important: it is the one thing between the world and your brain.

What do you think you would do better with, a blindfold or numb feet?
I have some interesting videos about this...!
Braking is the highest ground force you will come across in the running world. 
It occurs when your foot touches the ground ahead of your center of gravity.

Runners complain that running downhill hurts. That is because they are braking. Running downhill is when you feel braking the it most. 

Land ahead of yourself -> Overstride -> Brake -> High Impact -> Trouble.

Shorten your stride, land under your center of gravity: Running downhill will be very FAST and then you know you're in the right path.