First thing is controlling your speed by sitting up to let your body catch the wind, may slow you down by 10 mph.
Pedaling down hills can help make the bike more stable instead of coasting down on the descent. This can be accomplished by using a bigger gear.
Try not to use the brakes continuously on long descents. This could cause the rim to heat up and cause damage to a carbon rim braking surface or a tubular tire to come off the rim. Apply brakes briefly to slow speed in order to keep the rim cool.