The most important topics forex traders need to understand is risk management.
Specifically how to control risk and the importance of a good risk reward ratio.
Traders need to focus on doing what they can to reduce the size of their losses when they happen.
Trading on a margin account you can easily lose all your money if a trade goes against you and you have have a too big position size for your account.
At the same time, traders also need to optimize their trade size to make the biggest possible profit according to their risk preference on each trade.
High potential return equals high potential risk. That's why risk management is important.
By knowing how to manage risks traders can play the long game and consistent profits.