I think the most difficult lesson is, Life is not fair. Once you accept that, everything else should fall into place.
And that’s the one that so many of today’s young people, especially young, white college educated women, struggle with. They have been taught that the world of the white man is horrible because it does not produce fair equitable results for everyone. Therefore, it must be destroyed and replaced with the socialist utopia where everyone has what they and their families have. What they don’t understand is that’s not the equality the Left has in mind. There is more than one way to make everyone equal.