I have never been afraid of decending. I learned real early on how to steer the bike with my chin almost touching the handlebars. Decending fast is all about control. tuck both knees into the frame, tuck both elbows into your body, put your feet/pedals parallel to the ground and drop your body to the top bar, hands in tight toward the stem. Never use the brake if you don't really need to, just moving an arm out to the brake lever will scrub off an incredible amount of speed. One thing to note, these speeds are really only possible on fairly straight stretches of downhill, or just very gentle sweepers. I am not a great climber, but most of my riding buddies at the time would always wait for me at the top simply because they knew the could get personal best deceding times if they could hang on my wheel on the downhill side.