Star Wars: The Last Jedi - Predicting The Plot In 10 Steps
9. Luke Refuses To Train Rey
Again, it's clear that Luke is feeling completely destroyed by the failure of his Jedi Academy. The man has forced himself into exile on a remote, desolate island!
It's said that Luke began training a new generation of Jedi after Episode VI, with Ben Solo, the son of Han and Leia, among them. Ben eventually turned to the dark side, became Kylo Ren, and the other Jedi Luke was training were killed as a result.
Taking all this into consideration, why on Earth would he want to (potentially) put himself through that torture again? To impart all his wisdom and knowledge, only for it to be used against him, and used against innocent people.
Imagine you poured 200 hours into The Witcher 3, then your save became corrupted. You probably wouldn't feel compelled to start the game all over again. Remember, it's speculated that Luke will train Rey, but not confirmed in the slightest.
Also, Luke's refusal to train Rey will give her a motivation for the way she acts later in the film...