I think that mentoring by a more experienced trader helps a novice trader to develop in the right direction, minimize their risks and eliminates some of the mistakes that a beginner can make.
Its true and its important to have a mentor if possible. A mentor that is someone whom you know and having enough experience to implore. That way, you can minimize your mistakes in trading and and so with losses. If you cant find a good mentor, you can also learn from self discovery and researches. There are tons of information here and even in youtube.