The most important thing is that the trader is successful enough in the long term, so that most of the trades are successful and a few losing trades do not greatly affect their results.
To succeed in long term trading, managing their trading capital is most important. If they always use all capital for trading, they can win big or lose big and there is possibility to lose all their capital one day.
Avoiding the risks that can be avoided is essential - it's all about risks-management and the responsibility put into it, along with the clear goals in mind when you start your trading session each time.