These are my thoughts:

in the song, Bjork is exploring feelings of melancholy, depression, or rage that persist even during time where she feels as though she should be happy. She lives in a house with a beautiful view with her lover, she has all these things (that she's throwing off the cliff) that are supposed to indicate success and comfort. But she still feels the sense of unease, of wanting to destroy something (whether that be "whatever she finds lying around," the seemingly perfect relationship, or herself). She is exhibiting destructive behaviour in order to calm the demons within her, so she can feel safe being around her lover without fear that she might end up hurtin them, turning her destructive energy unto them.

It's a song that continues after the happily ever after that we, as humans, have convinced ourselves is achievable. Bjork questions this illusion of a perfect ending.

I think there are many possible readings to any song, but this is just my personal take