Ow ow OWWW! Falling down stairs is second only to falling into moving machinery for least favorite things to do. I think I would rather have an eye poked than break a neck ... I only have the one neck, you see. i think stairs are a conspiracy by young, healthy people.
Good luck with taking fewer dives!
Seriously, the rule of thumb is pretty good: let your butt go straight down, and nothing needs to flail around or dent the floorboards. I usually cheat and put an arm down to break the fall, which does risk a wrist sprain, but makes me feel like I'm doing more to control the fall.
Probably that's why they taught us to use the fake-casual "falling!" announcement, so we would feel in control. The first time I fell by surprise while mostly paralyzed, I let out such a high-pitched, loud "WHOOOPS!" that a whole gym-full of more experienced people had good belly-laughs.
While I was in the rehab, I was the LUCKIEST guy there. Other people were permanently paralyzed with broken backs, or had degenerative MS. I had a good prognosis.
I was considered 90% likely to recover 90-100%, like most GBS patients (Guillain-Barre syndrome). Unfortunately I beat those odds so that I was "the other 10%". Usually being "the other 10%" is an honor, but in that case, an inconvenience. It's really minor compared to any real handicap.