Happiness versus Desire
We are all unhappy to some extent, or at least less than perfectly happy. And we all have desires of various sorts: sex, cars, money, status. The connection seems obvious. "If I could have ... then I'd be happy" we think. But it isn't true. As we well know from following the lives of the people who have the things we want.
Our happiness and our desires come, indirectly, from our genes. They send us happiness when we are doing something that suits them and they want us to keep doing it. They send us desires when they want us to take risks to achieve something that suits their purposes. However their purposes aren't directly to make us happy, and can easily lead us to a less happy place. The fact that our genes don't want to make us happy, doesn't mean that we can ignore them. It is however possible to understand our genes well enough to get to places where they stop prodding us to do something new, and instead encourage us to keep on with what we're doing, which they do by making us happy.