system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some near death experiences cause PTSD and some cause other people to live their best lives after.
gpt
Resiliency.  There's the notion of "window of tolerance" in psychology.  For someone with a large window of tolerance and good support, getting a ton of stress/fear and overwhelming the system for a short while can make them stronger, if they get back to their tolerance level soon after. Anti-fragility is another label. 

However, those with a crappy childhood (ie, many Adverse Childhood Experiences), the window of tolerance is small, self regulation is harder, and being thrown into a completely overwhelmed state is beyond their ability to get back to regulation.  One theory is the overwhelm is stored in the body and dissociated from, but we're still understanding this.

The first example is like testing steel and not bending it.  The second is actually bending it so the steel is fundamentally weakened.

What's unfortunate is that those with crappy childhoods usually get less support than those who have "good enough" childhoods, for a number of reasons.  The Western culture also has more emphasis on roughing it out alone.