Going through any traumatic experience will change you in ways you can't imagine until it happens. It moves the bar to a point from which it will probably never fully come back, something will always be there to serve as a reference. To anybody who went through trauma looking at other people's lesser trauma looks like "trivialities". But it never works the same way the other way around. You can imagine lesser trauma but not really greater trauma.

> happiness requires much more than just not dying

Probably not for the people who don't have just the hypothetical appreciation of being alive but actually "cheated" death when it was all but certain.