Once, a while ago after i had been studying about 2 years, i was helping unload the groceries from the back of my mom's Dodge Durango (its a heavey car, haha) and my head is probably about 1/2 a foot from the top of the hatch, and all of a sudden my little brother pulls it down to shut it; onto my head. So i crumple to the ground the second i feel the pressure on my head and just land with perfect ukemi, leg under me, and hands spread out to my sides. And my body had done this subconsiously, haha, i just kind of reacted, and i remember looking up from the ground wondering what the heck happened
So i guess what im saying is just that if you DO fall, you arent going to know its about to happen, but i guess just the main thing is DONT freak out while your falling, its usually easier just to fall and get back up than to try and stop your fall with an extended hand and break a wrist.
And no, its not much different; but if you are worried about it, why not try practicing falling and rolling on concrete or blacktop?