Personality traits like extraversion and neuroticism can affect how happy or satisfied people feel. Extraversion traits like being outgoing and sociable can lead to positive feelings, while neuroticism traits like being anxious or moody can lead to negative feelings. These traits can predict how happy someone will be over a 10-year period, showing that it's not just temporary moods that affect happiness. Different theories can help explain why people feel happy, with both personality traits and how people adapt to their circumstances playing a role.