During deep sleep, the brain clears residue that distorts perception. Without this reset, the mind carries unfinished noise forward, which often reappears later as dream imagery.
Experience is reviewed and reorganized rather than stored intact. Fragments are sorted, stitched, or released. Dreams tend to surface while this rearrangement is taking place.
Emotional intensity softens as stress activity settles. Feelings that could not be integrated during waking life return in clearer, symbolic form during sleep. Dreams arise where these processes overlap.