During sleep the brain might be constantly simulating past experiences, movement, and altered consequences as a possible "re-training" model. Some of those sim

During sleep the brain might be constantly simulating past experiences, movement, and altered consequences as a possible "re-training" model. Some of those simulations may have outsized emotional moments which "jolt" our consciousness enough to perceive the dream. Painful memories are often an easy target for these simulations to use because they have more definition that many other memories.