There's a really powerful documentary on Netflix called 'Happy' which I recommend. I've watched it twice and used a notebook to make myself notes. Researchers present findings on happy people (and unhappy people) from all over the world.

Here's the really hopeful message:

About 50% of a person's happiness level is genetic
Only 10% is related to income level/lifestyle

That leaves 40% that is under our control The documentary lays that out in more detail than I can here but a lot of it is about intentional activities...exercise...helping others...novelty etc

When we aren't happy, we can work on our happiness skills to improve them... just as carpenters work on their carpentry skills and athletes work on their running time etc