You are missing 50% of your life. And you’re not alone: Everyone is. I say this confidently, even without knowing who you are, or how your brain might be different from the last one we tested in my lab at the University of Miami, where I research the science of attention and teach cognitive neuroscience courses.

Over the course of my career as a brain scientist, I’ve seen certain universal patterns in the way all of our brains function—both how powerfully they can focus, and how extraordinarily vulnerable they are to distraction—no matter who you are or what you do. I’ve had the opportunity to peek inside the living human brain, and I know that at any given moment, there’s a high probability that your mind just isn’t here. Instead, you’re planning for the next item on your to-do list. You’re ruminating on something that’s been bothering you, a worry or a regret. You’re thinking about something that could happen tomorrow, or the next day, or never. Any way you slice it, you’re not here, experiencing your life. You’re somewhere else.

Mental time travel is one of the biggest culprits degrading our attention. We do it all the time. We do it seamlessly. And we do it even more under stress. Under stress, our attention gets yanked into the past by a memory, where we get stuck in a ruminative loop. Or