~snip
People especially newbie ignore this stuff. Their goal is to have huge profit so they often tend to risk a huge percentage of their portfolio. They don't think about any risk and just think of the outcome if the market favors their side. They will just realize their mistake when their portfolio is more than 50% down.
Learning those strategies requires strong discipline to control their emotion which is the most important for me to avoid huge loss in trading. Even experts sometimes forget their trading strategy because of greed.
Position size is incredibly important in order to determine if a trader will become successful or not, after all even if you had a strategy which could give you profits and you were completely sure about it as you backtested your strategy, all of that will be for nothing if your position size is too high.
This is because regardless of how good your system really is there is no system that wins all the time, so you also need to prepare yourself to endure several losses in a row, but if your position size is too high then you will lose a lot of money to the point it will be impossible to ever recover it no matter how long you trade.