Psychology
We have been nurtured and brought up to do right things. As such, we do right things. In a sense, we cannot be wrong whatever we do. The trading proves us to be wrong about 50% of the time. But our psychology wont allow us to be wrong in our deeds. Hence we try to force on our trades to be right even though they are wrong. This is the most important aspect we need to tackle before embarking on trading.
We should train ourselves to be looser on 50% of the decisions we make in our trading. Loosing trades are to be closely guarded consciously by taking small losses. This takes much time to sink into our subscious mind which is responsible for most of decisions.
You will be wrong in the trade. What is the cost of being wrong? Every trade should be consciously approached as it is going to be a looser.
Trading is a beast which tricks you to do nasty things. For example, we average a loosing trade instead of killing it when it hits Stop Loss. And this proves to be a winning trade. It makes you to do average a loosing trade. As it goes, your 10 trades will turn into profits. One day, you will get struck in a wrong direction, you will keep averaging the trade, and it will never turn up...and you will loose heavily more than what you made on 10 trades and somemore.
First thing to master in trading is to manage loosers effectively. No matter what market does, you need to exit on SL hit. The market may move in your direction after SL hit, but that is the trick which succumbs you into large and big looser. This should be guarded effectively.