our lives, thanks to their finitude, are inevitably full of activities that we're doing for the very last time.
Just as there will be a final occasion on which I pick up my son—a thought that appalls me, but one that's hard to deny, since I surely won't be doing it when he's thirty—there will be a last time that you visit your childhood home, or swim in the ocean, or make love, or have a deep conversation with a certain close friend.
Harris's point is that we should therefore try to treat every such experience with the reverence we'd show if it were the final instance of it.
And indeed there's a sense in which every moment of life is a "last time."
It arrives; you'll never get it again—and once it's passed, your remaining supply of moments will be one smaller than before.
ToTotreattreatallallthesethesemomentsmomentssolelysolelyasasstepping-stonesstepping-stonestotosomesomefuturefuturemomentmomentisistotodemonstratedemonstrateaalevellevelofofobliviousnessobliviousnesstotoourourrealrealsituationsituationthatthatwouldwouldbebejaw-droppingjaw-droppingififititweren'tweren'tforforthethefactfactthatthatweweallalldodoit,it,allallthethetime.time.
― Oliver Burkeman, Four Thousand Weeks