One of the be-deviling aspects of personality structure is that there many structural divisions of personality in existence.
Some structures focus on personality traits (e.g., extraversion-introversion; neuroticism-stability), other structures focus on divisions of personality according to their processing areas (e.g., motives vs. emotions). Still others refer to developmental levels, such as Freud's id, ego, and superego.
How is one to make sense of these competing models? Are they all possible? Are their contradictions an embarrassment?
The answer can be resolved using a systems approach. See the Addressing Personality Structure page for a discussion about structural models and how diverse models can coexist (although not all such models are equally good).