Being simulators, demo accounts can only prepare you for the common market conditions. But as the market is always moving, you may not really see the same market conditions when you go live. Once you are done with practically testing what you learnt from your course, book, or wherever you did your learning, keep some capital aside, losing what won’t hurt you.
When they say that you must do your trading step by step, they mean that you must leave no stone unturned that could become a stepping stone towards the success of your career. My demo account has proved to be a stepping stone in my career. I always check my strategies on my demo account to ensure that I am making the right moves.
the demo account performance not works at early stage , its a very common stage , but without demo the complete trading life will not fill up at all.