When it comes to a demo account, it is a gift from heaven. Here you can test how well your predictions work, you can improve your strategies without risking anything in the market, and you can refine and improve the emotional side of your psyche to better suit the market itself. Just make sure that you also test your results in demo trading with a period of real trading with a demo account.
Even if they have the same initial conditions, their personalities and strategies influence the trading process greatly