Why is it so easy to forget where you’ve left your keys every morning yet so hard to shake the most embarrassing memory of flubbing your lines in the second-grade play? Strong emotion undermines our ability to forget, even when we want to, according to a study from the University of North Carolina at Chapel Hill. The embarrassment—or sadness, glee or any strong emotion—that was part and parcel of the experience causes our brains to forge connections that something mundane, such as being told a phone number, does not, explains Keith Payne, Ph.D., study author and assistant professor of psychology there. “These memories become more ingrained precisely because they have this emotional aspect.” But even unshakable dark memories have a bright side: Remembering bad experiences helps you avoid their recurrence. —Mego Lien