Breakin' All the Rules (2004)

Quincy Watson (Jamie Foxx) has been having a tough time. After being abruptly dumped by his fiancée (Bianca Lawson), he decides to quit his job as an editor. Remarkably, Quincy manages to turn things around when he pens a book about ending relationships. While the book leaps to best-seller status, it gets him into trouble, particularly after his cousin Evan (Morris Chestnut) gets inspired to leave his beautiful girlfriend, Nicky (Gabrielle Union), who later falls for Quincy.