If trading psychology only meant taking control of your anger, and rage then you could simply say it is like an anger management class for forex trading.
No, trading psychology is much more than overcoming negative emotions like greed, vulnerability, fear, and other stuff.
When one develops their trading psychology, they also develop a growth mindset, you develop confidence when making plans. Developing a trading psychology brings you out from the uncertainty you face when trading, whether it's the confusion of which trade to enter or what timeframe to set.