system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does letting your body go limp protect your body/give you a higher chance of survival than bracing when in a car crash or falling off a cliff etc?

I’ve heard stories of people going ‘rag doll’ and surviving these types of things vs people bracing and not surviving.
gpt
Bracing usally places long bones ( arms , legs) and other large support structures ( pevlis, spine) in line to take the full force of the impact. This usally ends up causing multiple fractures. This causes massive internal bleeding, and if enough of that happens  for too long you die. 
Think of it as being at the beach by the ocean, a waves are coming. If you try and stand there braced you can stand up to the smaller ones but at a certain point a big enough wave will knock you over. However if you lay back relax and float the waves will travel through and around you and a big wave that would have knocked you over does very little to you. Of course there will eventually be a big enough wave, or you will be in the wrong spot during a wave, that you will still get knocked around no matter what.