The setting doesn't affect the mood because the setting is his house and his school. Nothing really goes on in these places. Steven's little brother, Jeffrey affects the mood mostly. Jeffrey annoys Steven at home all the time. There was also a time when Jeffrey had  a nosebleed and Steven was blamed for it. His parents thought that Steven had punched Jeffrey in the face. They wouldn't even talk to him and his name went from "beloved first born" to "that one." This upset him and secretly he was worried about his brother. Through out the whole school day, he was eating tic tacs to calm himself. This  changed the mood from cool and calm to upset and stressful.