In-Universe Catharsis

In Real Life a big part of why we love Media is that it is cathartic. It is fun to blow off steam shooting up Mooks, crying over a Tear Jerker, enjoying a Sadist Show, etc.

There is also a more serious form of catharsis where psychological ills are healed through ceremony or painful experiences. Basically, usually as a major plot point, a character either seeks or inadverdently goes through an experience that normally only a Nightmare Fetishist might seek, and it helps them deal with a medical, psychological, etc. condition. When a story does this for a reader in the real world, it's a Subjective Trope. When it occurs In-Universe, it's less subjective.

Anime and Manga

 * In Karin, gloomy Fumio becomes an energetic optimist after being bitten by Karin.

Film

 * The Horse Whisperer ends up helping both the horse and owner this way.
 * In Analyze This, Robert De Niro shooting the couch probably counts, as it was likely extremely cathartic for his character.
 * Star Wars Expanded Universe: Aaron Allston's X-Wing novels are full of this. Most notably, Myn Donos' arc in Wraith Squadron contains at least two distinct and separate examples of this trope.

Literature

 * In Kushiels Dart, Phedre goes to the temple of Kushiel to atone for her role in the death of her master and the things she had to do when a captive of the Skaldi. Kushiel himself is said to be the patron of a very harsh mercy, attended by masked priests and priestesses who inflict painful rituals on those who come seeking atonement.

Live Action TV
""By G'Quan, I can't recall the last time I was in a fight like that! No moral ambiguity, no hopeless battle against ancient and overwhelming forces! They were the bad guys, as you say, and we were the good guys. And they made a very satisfying thump when they hit the floor."'"
 * The Star Trek franchise has touched on overcoming psychological issues through cathartic experiences on multiple occasions.
 * Star Trek V: The Final Frontier: Sybok uses his unique ability to share with and help conquer a person's greatest emotional trauma to gain the trust of most of the crew.
 * As did Babylon 5; in one episode, a mentally disturbed Earth - Minbari war veteran reenacts arthurian legend with Delenn as a means of finding peace.
 * Earlier in the same episode, the same veteran gets in a fight with some Downbelow thugs, and gets helped out by G'Kar, who recounts how it felt shortly afterwards:

"Marcus Cole: Well, they said I was carrying around a lot of repressed anger. Lennier: And? Marcus Cole: I'm not repressed anymore!"
 * In another episode, Marcus Cole has just finished beating a room full of thugs senseless in a brawl.


 * The Dark Truth on Eli Stone can be used for this, if this troper remembers correctly. However, it's usually used for other things.

Video Games

 * Mass Effect 2: Jack is not what you would call a well adjusted individual, owing in no small part to the horrific experiments performed on her. The mission to secure her loyalty has you guiding her through the abandoned facility where these experiments were performed and dealing with some of the remnants of her past, before setting a Big Bulky Bomb in her old cell and blowing the lab to smithereens. Afterwards, she becomes... well, slightly less Ax Crazy. The achievement you get for completing the mission is even called "Catharsis."
 * Also, after taking down the Shadow Broker and saving Feron, Liara is much more like the person she was in the first game.
 * Max's monologue in the normal ending of Max Payne 2 (concluding with "I had a dream of my wife. She was dead. But it was all right.") suggested that Max underwent a catharsis after, finally breaking away from the self-destructive path that Michelle and Alex's deaths put him onto. Part three says otherwise.
 * At the beginning of Ace Combat 5 The Unsung War, Nagase is saved from a very embarrassing defeat by Captain Bartlett Taking the Bullet for her. The guilt over this accident follows her throughout the game until the mission "Ice Cage" when she finally completes her almost two months-long crash (while looking for POW Bartlett, no less). She is significantly less troubled after she is rescued, even though Bartlett isn't found.

Real Life

 * The dictionary definition is here and here.
 * The Other Wiki defines it here, mentioning that some modern psychiatrists call this closure.
 * A number of ancient societies had some form of ceremony that was intended for this purpose.