Breaking up is hard to do--at least it seems that way for Madonna. The pop singer's attorney filed court papers Wednesday to withdraw her petition to divorce Sean Penn, a deputy clerk at the Superior Court in Santa Monica confirmed Thursday. Madonna filed for divorce on Dec. 4, citing irreconcilable differences in the turbulent 2-year-old marriage. Madonna, 29, and Penn, 27, were married Aug. 16, 1985. Madonna reportedly decided on divorce after Penn suddenly showed up at her apartment during the Thanksgiving holiday after an unexplained four-day absence.