1. Infidelity and Regret: The song suggests that the protagonist's partner was unfaithful, leaving them feeling betrayed and devastated. The chorus revolves around the line, "I never, never want to see you walking away from me again," indicating a desire to prevent further emotional harm.
2. Obsessive Thoughts and Jealousy: The protagonist grapples with obsessive thoughts about the past relationship, imagining their ex with someone new and feeling a burning jealousy. The lyrics, "Just when I thought I'd found a way, and I'd found my way out, you drag me back in," illustrate the struggle to move on.
3. Emotional Vulnerability: The song reveals the protagonist's emotional vulnerability and longing for the past. They express a desire for things to go back to how they were, even if it means ignoring the hurt they've experienced.
4. Self-Reflection and Blame: There's a sense of self-reflection and an admission of shared responsibility for the relationship's demise. The chorus' repetition of "It was only supposed to be fun," suggests that both parties may share some blame for the situation.
5. Dual Perspectives: The song seems to offer dual perspectives, with the narrator expressing their thoughts and feelings while simultaneously providing a critical and perhaps disapproving view of their own behavior.
Overall, "Mr. Brightside" explores themes of betrayal, jealousy, regret, and emotional struggle, capturing the complex aftermath of a failed relationship.