The moods of the people living in the attic reflect the difficulty of having to live under such horrible circumstances. The secret annex is cramped and crowded, and this leads to tension between the people living there. They aren't able to breathe fresh air by going outside. Being forced to stay inside, they have to resist their natural impulses of behavior. The moods of the occupants determine the atmosphere of the secret annex itself. Through their moods, we learn the traits of the characters, whether they are selfish, shy, or difficult to get along with. Their moods decide what kind of day the occupants will have.