There is no purpose. As numerous scientists have put it, if you could rewind the tape of evolution & replay it, the chances that Homo sapiens would once again evolve are vanishingly small. Something in the neighborhood of 99.5% of all of the species that have ever existed on earth are now extinct. There is no reason to think the fate of our species will be any different. One can try to make of her / his life whatever s/he wants. But, in the end, we're all just "dust in the wind."