Rapid eye movement sleep—where most dreaming happens—takes the sting out of emotional experiences. When we’re in REM sleep, all stress-related neurochemicals are absent from the brain—the only time this happens in a twenty-four-hour period. According to Matthew Walker, during REM sleep the brain reactivates emotions and problematic memories and brings them back to the mind through reflective dreaming in a neurochemically safe, stress-free environment.
