It’s finals week during your last semester of college, and you realize something terrible: You have to take the final exam for a class you forgot to attend all semester. How could this happen? How could you be so irresponsible?

You jolt awake with a gasp, and it takes you several seconds to remember something: You finished college 20 years ago.
So why do you keep having dreams like this?
You’re not alone, according to the Atlantic. Dreams about school stress are incredibly common among adults, even decades after they finish their formal educations. While some wake in a panic about a class they never attended, others dream about exams written in hieroglyphics or showing up to school in their underpants.
As Harvard dream researcher Deirdre Barrett explains, these dreams often occur when we’re anxious in our waking lives, and reflect formative early experiences of success or failure or interactions with powerful authority figures.
But why do we have these dreams over and over, and why are they the same in so many people? Some researchers say that it might be an evolutionary advantage. Our prehistoric ancestors were surrounded by threats, and dreams provided a safe space to practice detecting and evading predators. Unfortunately, in our modern environment and culture, this mechanism has evolved with us to create dreams about finding out that you must return to high school at age 47 to re-take calculus.