Difficult to say; some may just have to do with the basic temperament upon which people build their experience. For example, as in a family where everyone was raised by the same parents, under the same circumstances and opportunities. Here, it would seem that people simply have different capacities to — for example — face the difficulties they face.

Then, of course, there are the things that "happen TO you." Someone you care about dies. The company you work for shuts down. You have an accident and have difficulty walking, or lose an arm.

Without a doubt, the Human condition is very complicated!

=^..^=