Live account is what will make you have competence it is not demo. Demo is for back testing your strategy to see how it will work if you are making real deposit but trading live is where you can be able to test how you will behave if you are trading. Many people will not take demo serious because they know that if they lose they will not lose real money.
Demo accounts can actually be used to master your strategy and build some level of confidence. Although there are people who because the money there is free money or should I say virtual money, they it may really take them time to master self control and risk management, because they can really feel the impact of every single loss, and that’s why real account can also help one to master their strategy faster.