"How is it possible to move through the world with your eyes open and not be devastated by what you see?"

Because as you age, you become aware of long term patterns in the story of being human, and realize that everything that you see today has been repeated over and over again in history.

A cursory look at literature and history reveals that the sheer brutality was far worse in the bad old days all over the world, and has humans move forward in time there are a lot of improvements in their overall quality of life. If I look at ordinary (and not the nobility, titled class) people's lives 100 years ago, 500 years then 1000 years ago, life looks pretty good now.

There is not much new under the sun. It has all been done before.