I have this personal theory that some time after an external stress-related impulse (be that negative - ww2, cold war, becoming paralyzed, etc, or positive - inheriting money, winning the lottery, not having to work for the rest of your life, finding the love of your lufe, etc), the brain adjusts and one comes back to the baseline of their perceived normal stress level. And that’s why we see people who are always happy and seemingly stress free despite having nothing, and ones that always seem stressed to the max despite having everything