The idea that personality never changes once you reach adulthood continues to be challenged by study after study. The well-known Five Factor Model, or Big Five, with its scales that measure neuroticism, openness, extraversion, conscientiousness, and agreeableness, wasn’t designed for anything other than one-time, stable measurements. Maybe you’re feeling pretty calm and centered today, so if someone gave you a neuroticism measure, you’d come out smelling like a rose. If you had to answer a typical neuroticism scale item, you’d be faced with making general ratings about how you “usually” are. What you can also learn is that no day is ever all good or all bad in terms of personality.