Suggest me a book about “The Grind”

I’m looking for a book, maybe fiction, sci-fi, fantasy, that is all about the training arc. Sometimes these topics can be toxic and that’s kind of what I’m looking for. Think Whiplash, Rocky, Creed. Books like this that I’ve enjoyed are the Cradle series, Rage of Dragons, Berserk(?), and to a lesser extent Enders Game. Thanks !