When you trade with an amount you can afford to lose, your emotions will always be in check, and as such, your peace is secured, you wouldn't be making outrageous emotional decisions that may warrant you to start losing money.
It's good to think of it before a beginning but it doesn't mean you will feel good when you are facing loss or complete loss of your original trading capital. It's never easy for new traders to afford losing all original capital. This lead to another wrong thinking to "Revenge the market" that results in more losses.
Newbies can start with a good thinking "afford to lose trading capital" but in actual trading, emotion and psychology will be so hard to control and will affect trading decisions. Newbies have to trade a lot to control emotion and psychology, it's only achieveable with time and experience. If you feel it is hard to achieve, just DON't trade.
Calmness is very important in trading, because it will affect the decisions we will take. Once we are affected by emotions, everything will fall apart. It is better when we feel uneasy or start to feel anxious, it is better for us to stop for a moment to restore unstable emotions. Some people experience losses not because they lack knowledge, sometimes they experience big losses because they force themselves to continue trading when emotions are unstable. Although we can be said to be able to recognize emotions, sometimes emotions come suddenly and will be very difficult for us to control, the choice is to stop for a moment.
In fact, while trading, how much more you calm keep your mind relax, you can able to do better research the market and trade fully correctly. Because in order to apply the right market research and the right strategy in trading, you must first keep your mind calm. Because if your mind is not calm, you can make mistakes in market research, and if the market research is wrong, you cannot use the right strategy, as a result you will have to face losses.
And during trading, you must have a tendency to stop at any moment, because when a trader loses, many traders continue to trade emotionally, not caring about how much they have lost, as a result they end up facing losses beyond their capacity.
So you must develop the habit of stopping at any moment, because this can save a trader from suffering big losses.