I think you need to risk your life once in a while, to really appreciate it, a little like those pesky squirrels that run out in the road and play chicken. I know I do.
And when I go fast, it usually is over pretty quickly. I think the more dangerous thing than high speeds, is simple lapses in attention. If something takes you by surprise on a bike, by definition it means you were not paying attention and or didn't react. When I go fast, what's on the road ahead has 100% of my attention, so I think that counts for something, as a positive safety factor.