The irony of abuse cycles
This memoir depicts life's most poignant and tragic dynamic. Ironically, people who are abused are put through a lengthy test by their fate to see whether they will repeat the abusive patterns they were taught, or whether they will do the painful, often humiliating work of choosing a new path for one's self. The test is even more painful because the pain of having been abused leads to greater experiences of distress which make unhealthy coping mechanisms and abusive tendencies all the more temping.
The slingshot liberalization
The conservatism of a patriarchal family ended up being highly ironic in Joy's life. Instead of emboldening her thoughts about rigorous discipline, Joy's relationship to her tyrannical step-father led her to abandon all faith in humanity, choosing to do things her own way. Because her major experience of authority structure (a child's experience of home) was chronically unjust in her development, she now fears authority structures and their tendency to corrupt over time. She is instantly slingshotted into her new adult personality, a liberal and open-minded hippie artist.
Drugs and karma
Drugs are ironic because they yield a wildly diverse "karma." Karma is found in the memoir when the writer comments on the ways her decisions led to manifestations in her fate that made her learn hard lessons. Drugs have the most paradoxically ironic effect on Joy's karma because they simultaneously bless and curse her; drugs send her into catastrophic experiences of hallucinogenic consciousness that permanently cement her point of view as "purely artistic," and they also lead her into an irresponsible lifestyle that leaves her in the poorly timed marriage and pregnancy that her mother's life was defined by.
Art as forbidden fruit
Throughout Joy's whole life, there is a situational irony around art. She longs to do art, but her overbearing and tyrannical step-father doesn't want to see messes and stuff. He chronically forbids her from practicing her craft so that when she is an adult, she does not have the ample benefits that childhood practice could have meant. Yet, this is her burden as an artist, to do art anyway, even when her life is painful and confusing, even when a child takes up all her time and husbands never understand. In spite of this, she lives to be the artist she has become.
Poetry and irony
To look at reality and to realize the undeniable beauty and artistry of one's life is called "poetry." Yes, poetry is also the real language that a person uses to categorize that essentially unspeakable truth, but before that language is ever truly poetry, a person's point of view has to turn to the sublime. There is a way in which the painful life of a true artist is like baking a cake in an oven whose heat is suffering. To the cake, it is meaningless heat and agonizing pain, but in the end, a person has accidentally attained the prophetic point of view that makes them eligible to write truly good poetry, eventually. Joy defines that process and basically lands on that point to close her memoir.