We are biological devices whose purpose in life is to replicate, as driven by our selfish genes. Happiness is just one metaphenomena that evolution opportunistically takes advantage of in order to achieve this purpose. It is a "purpose" in the narrow sense that algorithms that do not achieve it are removed from the population.
Over the course of a life, human happiness is primarily dependent on fulfilling the purpose as a replicator, genetically and memetically. We are sculpted in detail by being descended from billions of generations of successful replicators. There is much temporary, but little long term happiness in ignoring those forces.
Having a family, writing a book, creating a piece of art, or a functional invention, or a community. These are means of replication, to be optimized if you wish to increase happiness as a side effect.
What is the purpose of the system of replicators? Does it have one? Is it an end in its own right?
In my experience, people who see themselves as part of the pursuit of the purpose of the system are also able to find happiness even if they do not personally replicate in some obvious biological or memetic way.
> human happiness is primarily dependent on fulfilling the purpose as a replicator
With a species as complex as humans it becomes much less clear what being an effective replicator entails. Someone like Alexander Fleming (inventor of penecilin) has probably done more to augment human replication than a million typical humans. And of course this effect isn't limited to medical specialists. A more salient example would be any of the creators of or contributors to dating apps.
Over the course of a life, human happiness is primarily dependent on fulfilling the purpose as a replicator, genetically and memetically. We are sculpted in detail by being descended from billions of generations of successful replicators. There is much temporary, but little long term happiness in ignoring those forces.
Having a family, writing a book, creating a piece of art, or a functional invention, or a community. These are means of replication, to be optimized if you wish to increase happiness as a side effect.