I don't know what it means to be dark during the day and night.

The phrase "I don't know the darkness during the day" describes that a person has never experienced another person's life experience, so he can't understand his feelings. Because day and night can't coexist, they have completely different environments and can't understand each other. This sentence comes from Na Ying's song "I don't know the darkness of night during the day". In life, the state of "I don't know the darkness of night during the day" is true for most people, because everyone's living environment is different and things are different, so everyone has their own personality. These differences in experience and personality also determine that when we encounter things, we often have different ideas and handling methods, so we can "know the darkness of the night" in life, but we must also learn to be tolerant.