Many earlier psychoanalytic approaches to literature tended to analyze characters and/or authors in terms of such Freudian concepts as the id, ego, and superego. The id was often associated with emotion, the ego with rationality, and the superego with morality and/or conscience. Characters and/or authors were sometimes interpreted in light of conflicts between these three aspects of the psyche. This may give you something to go on as you begin to think about the poem you have in mind. For sophisticated criticisms of Freudian ideas, see the work of Frederick Crews.