Happiness is always a by-product. It is probably a matter of temperament, and for anything I know it may be glandular. But it is not something that can be demanded from life, and if you are not happy you had better stop worrying about it and see what treasures you can pluck from your own brand of unhappiness.
Young people are more hopeful at a certain age than adults, but I suspect that's glandular. As for children, I keep as far from them as possible. I don't like the sight of them. The scale is all wrong. The heads tend to be too big for the bodies, and the hands and feet are a disaster. They keep falling into things. The nakedness of their bad character! We adults have learned how to disguise our terrible character, but children, well, they are like grotesque drawings of us. They should be neither seen nor heard, and no one must make another one.