I used to be the same way. There are still hills that scare the bejezzus out of me... those are ones that are on gravel roads, with lots of loose, mushy gravel at the bottom. I might suggest using some of the mtn biker tips and tricks on descents until you feel better and more secure about your speed. i.e. move back a little and maybe even out of your seat a touch, with your pedals at 3 and 9. I'll be corrected if I'm wrong (I'm sure) but even though those are used to cushion blows and reduce the chance of endo, on descents they really do add to your ability to balance, and the way you 'feel' the speed, as well. I wouldn't necessarily reccomend it on a group ride, but while you're acclimating yourself to speed, I'd give it a shot.