"Inutiles regrets" ("Useless regrets" in English, but you probably already had figured that out), is the aria that Hector Berlioz has Aeneas sing as he prepares to leave Carthage and Dido. I'm linking you to a performance of this aria by Bryan Hymel. Here . There is much more I might say about this, but I hope to say it at JustSheetMusic soon and don't want to steal my own thunder here.