For those who haven't read this book, it posits that history is cyclical and the cycle in question is fairly short term.
I'll not attempt to give a synopsis here. It is a large chunk to digest and I recommend reading it.
http://www.fourthturning.com/I will give a link to an article which does a reasonable (IMO) job of describing the effects of a "fourth turning" as it applies to our current society.
https://medium.com/emergent-culture/and-fear-no-darkness-7079dc86d5f4#.bm5mxhd6wThis is not dystopian fiction. It is social analysis... You now have permission to run screaming into the streets.
In simple terms, the "cycle" has four parts, characterized as spring, summer, fall and winter with "winter" being the fourth turning. According to many pundits, we are beginning a fourth turning in world society.
Why we prep...
[edit] do note that since the cycle does recur, it is NOT TEOTW. It is change. Remember the Chinese curse: "May you live in interesting times".