According to Freud's thinking, nightmares can be explained like this. First of all, dreams are divided into explicit dreams and implicit dreams. Hidden dreams are the real intention of dreams, while explicit dreams are often disguised. In other words, the subconscious originally hoped to complete the hidden dream, but after processing, it appeared in the form of explicit dream. These disguises sometimes lead to chaotic dreams, and sometimes make dreams look the opposite of what they need. Secondly, some dreams realize the wishes hidden in the subconscious mind, which can't be perceived by consciousness for various reasons. In this way, some nightmare scenes are just unacceptable to the consciousness, but they are in line with the subconscious desire. For example, it is unacceptable for a boy to dream of his mother's death in reality, but it conforms to the Oedipus plot. Thirdly, some examples in Interpretation of Dreams show that Freud does not reject "thinking day and night", so he thinks that some nightmares are just the repetition of reality.
Simply put: 1. Dreams are external, seemingly nightmares, and imply content that satisfies wishes. They may not be readable when awake and need to be deciphered like a password. 2. Consciousness thinks it is a nightmare, but it actually satisfies your unconscious wishes; You will see things that scare you during the day, but you will dream about them at night.