The difference is that a professional trader, who earns, makes fewer mistakes. In addition, the losses of a good trader are always limited, he does not stay in position for a long time if the market goes against him.
I will say why that difference also happens. Professional traders usually work for someone else. They advice and they trade even perhaps, but usually not with their own money, so this is 2 things. Firstly, discipline is easier because it is someone else's money and you get a commission of every trade win or lose. Secondly there is a motivation to do consistent and small profits because you get more clients when you are successful. And as you say they always want to be flexible and not stuck in trades.