Songwriting suggestion: Write a breakup song — but not about a romantic relationship.
A long-term relationship has soured, and it's time to call it quits. Maybe it's a person breaking up with a heartless big bank, or giving up on a favorite product after its quality got worse and worse. Maybe your character is quitting a sports team, or sending a well-worn pair of boots to the trash.
Where to find ideas: Listen to some of the thousands of breakup songs for ideas on how to approach the subject.
Tips: You can do this as a funny parody of the breakup song genre, or you can make it completely serious. It's all up to you.
Here's the secret: A breakup always involves an inner emotional conflict within the person initiating the breakup. Play out that ambivalence and tension in the verses. Become decisive and single-minded in the chorus.