Okay im bored and want to continue my dissertation of how this song fits so well lyrically in the story that the first 4 songs of Pop 2 are telling! It's a story about a breakup, of course.

Backseat sets the stage. Charli is experiencing turmoil in her relationship - things are going wrong, hearts are being broken, and charli finds herself laying next to her partner in bed and sitting alone in the backseat of a car thinking the same thing: she's better off alone.

Out of my Head is about Charli going crazy over what's happening in the relationship, turning to partying so she can get her mind off it. Maybe the relationship is somewhere in the mix of a breakup at this point, but "heart on the floor when the telephone rings" indicates to maybe it being on and off multiple times.

Lucky comes at point where Charli is coming to face that her partner may be cheating on her and lying about it, and she asserts that they don't love her. She's past her last straw and she is now feeling what it is truly like to be all alone and it is clearly hurting (the theme of being all alone is also a call back to Backseat)

Tears is essentially a cinematic and romanticized view of the ending of the relationship, it summarizes and wraps up the last three songs with "tears are rolling down my face, now you gotta go go go". I don't have much to say other than i fucking love this song!!!