There have been a lot of surveys that have indicated that the average person in the third world is happier than the average person in the Western World.
Having been to much of the third world, my own observations concur (mostly) with the surveys......except that tragedy can be lurking around the corner for all those people. If someone gets badly sick, or there is a bad harvest, or civil unrest, or when many other bad things happen, poor people are much more vulnerable to the terrible effects of those calamities.
In most cases, poor people have experienced those sorts of crises - but if they come out the other side more or less OK, they go back to be happy again. With that being life for them and everyone they have ever known, that is their version of normal.
For people in the Western world, they grow up thinking that there should be some sort of safety net (that protects them from the bad things that happen sometimes). They also grow up seeing some people who are much better off than they will ever be. Unfulfilled hopes and expectations seem to cause resentment and unhappiness for many.
It is too bad that most "poor" people in Western nations can't afford to travel to the third world. It would do many of them good to see what being genuinely poor really looks like and how most of those people really do have (mostly) happy lives.
In my experience, happiness is something that mostly comes from within.
People often make the mistake of thinking that happiness is something other people should provide them, or that happiness is likely to turn up in a Fedex box, or that happiness is something you can buy in a shopping trip.