A Lesson in Defeat

The Mentor has a student with a great deal of natural talent. Unfortunately, that's a problem because due to that talent said student has become, or shows signs of becoming, an Arrogant Kung Fu Guy or Insufferable Genius.

The student needs to be brought down a peg, but the student has progressed to the point where typical discipline like lectures or punishments won't do a great deal of long-term good.

To this end, the mentor decides on a different tack: The student needs to fail. The mentor thus arranges a situation where his big fish is taken from his little pond and thrown into the big ocean.

A more benign version of this can sometimes occur if the teacher is doing it less as a preventative or punitive measure, and more because they believe a legitimate defeat will be good for them in the long run. As the saying goes, you learn more in defeat than from success. It could also be done to encourage the student to accept the possibility of losing more easily than he might have otherwise. Or, depending on the instructor, less easily.

The effects on the student can vary. If the student is an antagonist, it may lead to Defeat Equals Friendship with him and the protagonists. He may learn nothing. Or it may backfire and drive him further into the dark side of life. If a protagonist, the student may indeed learn the lesson and grow stronger for it.

This could also lead to a break with the mentor if the student learns about the situation. Possibly even some Rage Against the Mentor.

Compare Unwinnable Training Simulation, which is often done with this trope in mind. The difference is that the Simulation is done in controlled circumstances while a Lesson in Defeat can be done in a real-life scenario.

Anime and Manga

 * This is the primary reason for Master Roshi's assuming his "Jackie Chun" Secret Identity in the Strongest Under the Heavens Martial Arts Tournaments in Dragon Ball. He wanted to prevent Goku and Kuririn from getting big heads by progressing too far too quickly.
 * Toraji, the Kendo Club instructor in Bamboo Blade sought this for Tamaki. He wanted her to discover a rival among her peers who could equal her in order to make her stronger in the long term.
 * The spirit if not the specifics can be seen in One Piece when Dracule Mihawk defeats Zoro. Zoro definitely had the "big fish in a little pond" attitude when they met, though he was enough of a determinator to impress Mihawk. So rather than kill him, Mihawk defeated him thoroughly and encouraged him to see more of the world. Zoro's response to his crushing defeat was a tearful vow to never lose again.
 * During the S-Rank Trials in Fairy Tail, Natsu went head to head with Gildarts, the single strongest man in the guild short of possibly their Master. Natsu put in a good effort, but when he got a taste of Gildarts's full power he fell to his knees and gave up on the spot..

Comic Books

 * In Usagi Yojimbo, little Usagi is given a lesson by his master. He's ordered grow some carrots from some seeds. Usagi cannot make them grow at all, and considers stealing some carrots from a neighboring farmer, but his honesty gets the better of him and he reports his failure, expecting to be thrown out. His master was testing Usagi's honesty; the seeds had been boiled and would never have sprouted.

Film

 * In The Empire Strikes Back, Yoda sends Luke into the cave to experience the dark side of the Force. Luke declares that he is not afraid, and Yoda responds, "You will be."

Literature

 * A Song of Ice and Fire: The final lesson to become a new maester is to sit in a dark room with a tall, sharp candlestick. Many try to reach the wick, but are only rewarded with bloody hands and wasted time. The wiser new maesters wait the night. The lesson is that, though maesters strive to understand the world, there are some mysteries that simply cannot be uncovered.

Live-Action TV

 * The Kobayashi Maru test from Star Trek is the Unwinnable Training Simulation, designed to test how the students cope with a no-win situation.
 * During Star Trek II: The Wrath of Khan Kirk speaks of how when he was in the Federation Academy he found a way to beat the no-win scenario, something that gained him significant praise during his cadet years. Sure enough no matter how difficult the trials he faced were Kirk always found a way to win proving that the test was invalid as far as his abilities were concerned and he could always win. In fact the first time that Kirk can't find a way to win is when  as there was nothing he could do. This proved that Kirk was wrong, you can't always win and save everyone some times sacrifices have to be made.