There is no purpose to your life other than the purpose you choose to give it.
Is your goal the brotherhood of all mankind? Is your goal human flourishing? Is your goal a just and democratic society? Is your goal to serve some God or gods? The first cause of all of these goals, and any others you can think of, may be found in innate emotions and predispositions that exist because they evolved. They did not evolve for a purpose. They exist because at some time that was likely quite different from the present, they happened to increase the odds that the responsible genes would survive and reproduce. They are the foundation that gives rise to every single human aspiration, no matter how noble or sublime that aspiration is imagined to be.
There is no objective reason why the goals and aspirations of a Plato or a Kant are more worthy, more legitimate, or more morally good than the goals and purposes of a thief or a murderer. In the end, every human being on the planet is merely seeking to satisfy emotional whims that he has interpreted or tried to make sense of in one way or another. Any individual’s assumption that his goals are intrinsically superior to or more right and proper in themselves than the goals of others is a delusion. The universe doesn’t care.
What does that imply concerning what our goals should be, or what we really ought to do? Nothing! Nothing, that is, unless we are speaking of what some individual should do or ought to do to satisfy some idiosyncratic whim that cannot possibly be objectively more legitimate or praiseworthy than the whim of any other individual.
How, then, do we choose what are goals and purposes will be. After all, we will have them regardless, because it is our nature to have them. In the end, all of us must decide for ourselves. However, in choosing them I personally think it is useful to be aware of the above fundamental facts. The alternative is to stumble blindly through life, chasing mirages, clueless as to what is really motivating us and why. Again, purely from my personal point of view, that does not seem an attractive alternative. Blind stumbling tends to be self-destructive, not to mention inconvenient to others. I personally find it incongruous and disturbing to witness the spectacle of emotions and passions inspiring people to pursue ends that are the precise opposite of the ends that account for the existence of those emotions and passions to begin with.
I personally pursue goals and purposes that seem to me in harmony with the fundamental reason that my goals and purposes exist to begin with. In other words, my basic goal in life has been to survive and reproduce. Beyond that, I seek first to promote the survival of my species, and beyond that the survival of biological life in general. These goals seem noble and sublime enough to me personally. Our very existence seems to me improbable and awe-inspiring. Think of how complex and intelligent we are, and of all our highly developed senses and abilities. Look in a mirror and consider the fact that a creature like you could have evolved from inanimate matter. Think of the mind-boggling length of time it took for that to happen, and the conditions that were necessary for it to occur in the first place. Stunning! We are all final links in an unbroken chain of life that began with direct ancestors that existed billions of years ago. There are millions of links in the chain, and all of those links succeeded in generating new links, so that the chain would remain unbroken through all that incredible gulf of time. Under the circumstances, my personal purpose seems obvious to me. Don’t break the chain!
There is no objective reason why these purposes of mine are any more good, legitimate, or worthy than any alternatives whatsoever. They are not intrinsically better than the purposes of an anti-natalist, a suicide bomber, or a celibate priest. However, for personal reasons, I would prefer that, as others pursue their purposes, they at least be aware of what is actually motivating them. It might lead them to consider whether blindly breaking the chain, destroying themselves and harming others in the process, is really a goal worth pursuing after all.