When you realize your gonna fuck up... overshoot, undershoot you fucked up with your rotation or grab and you realize your gonna fall? Basic physic, your body is moving at high speed and falling will reduce his speed. What you want to avoid are big and strong impact on one part of your body (It will break). Alway let your leg get the first impact, but dont try to stay on them, roll forward or backward so the rest of your body rolls on the snow to decelerate your speed and in the end try to stay on back untill you stopped. In general, its a bit like when those parkourt guy land a big jump, first impact on legs, then try to roll and finish on your back once your on your back keep your hands close to you (a bit like a turtle on his back) never try to use your arms to stop yourself too many squishy bones you could break easily. Knowing how to fall realy help preventing injuries!!
I knew people were going to hit me up for that post, but sorry, no.
I have overshot/undershot some really big jumps that others have been carried away from, and have never come away with more than some snow on skin scrapes. That's from 10+ years of martial arts training/ falling.
The one time I tried to let my legs take the impact directly, I got bruised heels, which sucked.
You need to practice though, and then your body will take over. If you're scared of the ground, you're screwed.