Even a professional trader will at a time lose money. What differentiates a good trader from a bad trader is whether they are running on losses or profits on the long run.
Successful traders are not only measured by how much returns they get - they also need to know a lot about how to do analysis and how the market works.
It seems I will disagree with you here. It doesn’t matter how well a trader knows the charts, how well he knows about the fundamentals and his overall knowledge of the market. All these are skills needed by every good traders. But if anyone possess all these skills and yet do not win on the long run, we cannot say that the trader is a successful one.
As I said above, there are win days and loss days for every trader. If your winnings do not exceed your losses, you are not a good trader, no matter how skillful you are.
In the other hand, if a beginner trader who doesn't know much about analysis of trade, finds a way to win more than lose, that beginner is a successful trader more than a professional whose losses are more than wins.