I think this song is actually about a man speaking to himself. He has realized life is ephimeral, nothing lasts, and has decided to live on without wasting his short lifetime ("don't grow up too fast and don't embrace the past, this life's too good to last").
The lyrics are pretty much just that, but the music adds a sad, depressive vibe to this man's dialogue. He feels sad about his realization, but still accepts life as it is, and goes on.
Also, the second person talk and some lyrics suggest he might be giving advice to another, younger person.
Pardon if I wrote something weird or not too clear, I'm not a natural English speaker.
