Vocab

ebullience (n.) - high spirits; exhilaration; exuberance

"Events at Columbia University and the Chicago convention changed the mood of students from a hope-filled ebullience to a dark, protective aggression."

"The instructor’s ebullience encouraged the students to join her in her high spirits."

The antonym "aggression" suggests that the word ebullience means happy.

indifference (n.)  - Lack of concern or interest; unimportance

"The letter covered seventeen handwritten pages, its tone jumping from self-pity to anger to irony to guilt to a kind of feigned indifference."

"I wish I could say I was indifferent to these blogs that force us to spill our guts to the world."

Using my logic and background knowledge of the word indifferent from my father, I know it means lack of interest.

Catharsis (n.) - the purging of emotions or releasing of emotional tension; especially through some kinds of art.

"Partly catharsis, partly communication, it was a way of grabbing people by the shirt and explaining exactly what had happened to me, how I’d allowed myself to get dragged into a wrong war, all the mistakes I’d made, all the terrible things I had seen and done."

"I use my writing as a form of catharsis to release my thought and opinions without consequence because no one reads my journals."

Using logic I can infer that catharsis mean expression of emotion because O'Brian places further emphasis on explaining his feelings about revealing these occurrences.