Dreams are both a normal physiological phenomenon and a normal psychological phenomenon. Generally speaking, as long as it is not horrible, bloody, too anxious and nervous dreams, there is no negative impact on the physical and mental health of people.
1: as the saying goes: "daydreaming, nightdreaming" strange dreams are mostly related to my daily life wishes, imagination, memories, worries, thoughts and other mental activities.
2; the influence of internal and external stimuli. As the ancient book said "very full is dreaming with, very hungry is dreaming to take", overworked during the day, before going to bed to think y about the next day's work or entangled in the daytime unpleasant things, or physical illness, such as headache and fever, a part of the body discomfort and uncomfortable sleeping position, bedding is not soft and clean, etc., will have an impact on the dream. In short, as long as the second day to forget the dream, does not affect the work and learning and emotions do not have to care about him.