The lesson we learn from trading experience and articles we read are quite different, though the lesson from both are very important in trading but the mistakes of some beginners, they get much confidence in trading after learning only from books.
Experience gives the best lessons to traders, which beginners should never be in haste or be so confidence to trade with big amount of money by only gaining knowledge from reading books about trading.
Reading trading guides and practicing with demo accounts increases the confidence in some traders due to the level of trade winning they get while practicing with demo accounts.
That greed of thinking that the profit you made while practicing with demo accounts could have been real if the trade was conducted using real money is what always drags newbie traders to fund their accounts with real money and go in all hard, forgetting that there is a need to manage risk.