In "How Life Imitates Chess", Garry Kasparov wrote:

Every person has to find the right balance between confidence and correction, but my rule of thumb is, lose as often as you can take it. Playing in the open section and going 0-9 every time is going to crush your spirit long before you get good enough to make a decent score. Unless you have a superhuman ego, or totally lack one, a constant stream of negativity will leave you too depressed and antagonized to make the necessary changes.

I'm glad to see one commenter has already mentioned George Friedman – I got a lot of reassurance from this podcast interview in April 2020, and by reading his book "The Storm Before The Calm".

Just hearing someone articulate a plausible-sounding theory for why the current instability is expected/predictable makes it a lot easier for me to imagine different futures, even if I don't agree with all of Friedman's premises.

Bonus points to Friedman for writing his theories down in ~2019, just before the notable instabilities started.

I take issue with the authors here:

Won't the Amish or some other high-fertility, perhaps religious, sub-population expand to be as many as we need? For several reasons, no.

...

First, fertility in a high-fertility sub-group would have to be high enough (certainly above two, for example). We've already seen above that the "high fertility" of high fertility subgroups has been declining over the decades. High fertility used to mean 6 children per woman. Now it means 2.5. Before long, it may mean 1.8. Second, the children of high-fertility parents would have to be very likely to remain in their high-fertility cultural group.

I grew up in a small-town homeschooling community where large families were fairly normal, but many of the children did not go on to have many children, or homeschool their own children.

In contrast to that, I am now a member of a church where 4 children is considered a small family, and 12 children is considered a large family.

Many of the families are second-generation, and one of the topics of conversation is how to pass on a worldview that involves passing on that worldview recursively through the generations.

We're not Amish, but the Amish do seem to be doing a good job of this – per https://en.wikipedia.org/wiki/Amish#Population_and_distribution their numbers have been impressively consistent over the years. I don't know why the authors think that their next 100 years of growth would change from the last 100.

Now, it's going to take a while for their numbers to affect the global population. But it doesn't seem crazy to me that in a few centuries the world's population will be comparably large, and even more dominated by a few Islamic and Christian sects than it is now.