If it looks fast or feels fast it is probably slow!
Ever have that descent on your mountain bike where you felt like you were flat hauling?! At the bottom you were thinking (or telling a riding buddy), “wow, I nearly hit two trees, a big rock and that huge stump! I was flying!”. Believe it or not, despite feeling like you were right on the edge of your skill limits that was probably not near as fast as you could ride that descent (with your current skill).
If you look at rock four feet in front on you, you are going to be there (at the rock) in a fraction of a second, if you see the rock when it is twenty-forty feet in front of you you have plenty of time to go around the rock and you stay calm and relaxed.
This video reminded me of that. Notice how tense you get when the helmet cam is point down and how you almost breathe a sigh of relief when the rider looks further down the trail.