In The Great Gatsby, Nick is constantly in a struggle between admiring the lavish lifestyles of the rich of New York, and hating the superficiality and fakeness that comes with these. This ambivalence is a source of tension throughout the story.
However, towards the end of the novel, Myrtle's death, Gatsby's murder, and everybody's reactions to the events finally convince Nick that this lifestyle is a selfish, rotten one. He decides he wants nothing to do with it anymore, and decides to return home. By taking these actions, Nick is finally able to redeem himself, as he is able to establish that he is a different character from everyone else, and that he values more important things.