I haven't fallen on pavement since I was a kid jumping off homebuilt ramps. I've taken a few spills mountain bike riding, but always in leaves and grass...sometimes mud =)

Pavement riding is, in general, something I'm learning all over again. I used to everywhere as a teenager, but got out of the habit in college. Still went off road from time to time...but I started hit the roads and paved trails almost exclusively in the last year or so. Even then, it's been my MTB up to this point, and it's nothing if not stable

Long story short...I'm not used to falling down. It's something you just do a lot less of as an adult. As a kid, my knees were always scabby...now I'm just a big wussy.