Too much emotion.

When you have real money on the line and you see the movement go against you, the hardest thing to fight is fear. Being able to fight the urges most people have for self preservation is the biggest thing that successful traders have going for them. You have to learn to be mechanical with your trading. You took trades because you were hopefully confident in your actions. If you don't have the confidence in the trade, you should most definitely not be taking it in the first place. Doing so will only lead to emotional responses.
Let the trade run it's course and use proper money management. Plan your trade and trade your plan.