This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
Mental speed is demanded by all of these. However, being quick does
not guarantee success, because judgment is even more important. To
not be daring but rather to ride with a margin that leaves a feeling
of comfort rather than high risk, is more important. Just the same,
do not be blinded by the age old presumption that everyone who rides
faster than I is crazy. "He descends like a madman!" is one of the
most common descriptions of fast descenders. The comment generally
means that the speaker is slower.