I make a habit out of going down hills with my hands way up in the drops so I can get the most leverage on the brake levers, and my weight further back on the bike. In other words, I go down the hill anticipating that I might have to pull a quick stop. I also upgraded my brake pads because I have to deal with several steep hills on my commute. When I'm over 25 mph, I take the lane so I have somewhere to swerve if needed.

When I took driver's ed, I was taught that it's a good idea to not outrun your stopping distance. If you can't see over the next hill or around a bend, slow down. Going fast is exciting, but it's not worth having a wreck because you didn't see some obstacle. Riding a bike isn't any different. Save the fast stuff for when you have high-quality blacktop and unlimited visibility. The same rule applies to night driving and riding: don't outrun your headlights.