Time is that by virtue of which everything becomes nothingness in our hands and loses all real value.
Just because my dog Chunky gets excited when I come home doesn’t mean that he remembers me. Our view of nature is skewed in a way that if it must act in similar ways for us, or else render itself not useful.
Time in years, minutes, seconds is an invention of mankind, and it’s possible that time –in terms of starting and moving forward, possibly to its end– is also made-up. Perhaps only entropy exists.
Each moment of life is transitory and fleeting and quickly becomes the past—in other words, vanish into nothingness. The hourglass of our lives is slowly emptying. In response one might simply try to enjoy the present, but since the present so quickly becomes the past it “cannot be worth any serious effort.
So yes, Schopenhauer has a point, that it’s somewhat futile to live in the past, much like it in in the future, and since the present quickly becomes the past, enjoying the latter is incredibly difficult. But maybe there’s no such thing as ‘time’, and specifically, And maybe the future and past don’t exist, at least in any way that is important.
Chunky may not ‘remember’ me, or things he’s done, but they have shaped his character. So although dogs, box jellyfish or plant life might no re-live things in their minds in the form of a highlight reel like we do, what happened up to this point shaped them somehow, and caused them to do what they do right now.