It’s not entirely a state of mind. There is a qualitative difference between having an investment income approximately equivalent to a middle-class salary, and

It’s not entirely a state of mind. There is a qualitative difference between having an investment income approximately equivalent to a middle-class salary, and not having it. Certainly you can find people who would feel miserable with that amount of money, and people who could thrive on a small fraction, but it would give most people a freedom that very few ever get.