I think that being happy is an acquired skill. There are people who have a long list of things to be happy about, but if one little thing is missing, they will concentrate on that and be intensely miserable about it.
And then there are people who have the skill of finding one good thing they have in the midst of even the most disastrous circumstances and constructing an edifice of happiness around it.
Over the years, I have noticed absolutely no correlation between people's actual circumstances and how happy they were about their lives. To give an example, people in very poor countries often report much higher levels of happiness with their lives that people in rich countries. We often believe that if we manage to meet certain conditions (find the right person, make enough money, get into a great school, find the perfect job), we will finally be happy. However, people who didn't know how to be happy without the right person, the great school, the perfect job, etc., will find it just as difficult to be happy when they do acquire all those things.
Happiness lives inside us. So does misery. Everybody is the source of their own unhappiness and their own contentment.