I would genuinely be shocked if North Korean's aren't happy. They're basically told they live in the best place on earth, have no basis for comparison to believe otherwise, and the sphere of influence of any particular average N Korean is narrow enough that if they were sad it would basically be artificially constraining their sadness to ones about personal failures they probably would rather not believe they have.

It's not starving, not having healthcare etc that makes you sad so much I think as thinking others are getting it while you are not, or believing that someone is pulling something over you rather than the situation being in your hands. If you think you're doing the best you can and your own success or failure is up to you, it's hard to be particularly sad about the situation compared to someone in another position.