Many people try to find contentment, they search for it, which is why they fail to have it. Contentment, like patience, must be chosen, exercised, practiced. It is not something we bump into or something we find like a hidden treasure. It is a path, and it is attainable by everyone, not just those lucky few who land on the right square in life.
I would add that moderation is a key to happiness and contentment. People who live by extremes are very happy, at times. But then life is bad the rest of the time. It follows, then, that they get addicted to the high of happiness, and in so doing they forsake so many other things in life, even good things, to pursue the highs. And thus they ensure a life of chasing, rather than possessing, happiness.