Well, night and day are two sides of the same eternally flipping coin, an endless cycle, back and forth forever. But dreaming isn't the flip-side of death, life is. So maybe he's saying that "life is just a dream"? Or death is dreaming, but without light? Idk, but it's from a sleep/dream-themed concept album called Can't Wake Up. I highly recommend it, it got no attention anywhere but it's easily one of my favorite albums of the last five years.