Complex sentence: "The Blackest Day" is a post-breakup ballad, that follows the stages of grief, the first verse touches up themes of denial, notable in lyrics such as "I don't really wanna break up, We got it going on".
Split into simpler sentences: The Blackest Day is a post-breakup ballad, that primarily deals with the stages of grief. The first verse explores themes of denial, apparent in lyrics such as "I don't really wanna break up, we got it going on".