When we start winning we get anxious about loosing our gains .we close trades prematurely to capture the profits before the price starts to drop again.wereas we should be holding on to it and closing appropriately to maximize the profit.
Conversely,when we start loosing we hold on to the losing position longer in the hope it will turn upward at some point.we have the irrational beleif that we will reduce or wipe out the lose without proper re-analysis.
This can only occur when you are trading without target and vision. When you have a target and a strategy put in place, you will not be in haste to make decisions and exit the market prematurely with a little profit. Professional traders will likely not make such mistakes but newbies who sees trading as a get rich quick scheme. It's the reason why loses always surpass profits because you make little profit in interval and lose much regularly. One thing many of us is failing to understand with trading is the impact of our psychology. You can be expert in technical analysis but your actions are guided by your psychological nature. Some people are naturally excited with small profits and it reflects in their trading. Even when they have everything right, they can't hold on to reach their target before closing their order.