yeah this is what i find. i always put my hands down. it just seems to happen so quickly. so far my wrists have stayed intact.
If you can, I'd break yourself of the habit. That's how I broke my arm snowboarding (simple run, wasn't going that fast, fell backwards and bam, trips done.
two hours into a weeklong trip too...).
In the end though, sometimes falls just happen so fast you don't even have time to think.