I always wake up from a somewhat vivid dream of the world ending. Last one was where the world was ending in 3 days and it was gonna be in a way where we cease to exist and afterlife is empty darkness until the next round of our species, in a giant loop of start to finish.
i think dreams are like rewinding and storing memories and stuff. f i watched something like sailor moon, then my dream would be related. Or if you think about something very important for the majority of the day then you think about it in your dreams.