This example shows how human nature leads to traders taking too much risk on their downside and being too conservative when in the black. Think about this - its an extremely important lesson.
I have also noticed that a trader trading profitably changes their style and approach after one to a few big losses. The avg profit of their trades falls 30 to 70% and they end up taking the same big losses.
ALWAYS PLACE A HARD STOP if you are a new trader and/or lack discipline. It forces you to get OUT of bad trades. Many traders would be profitable if they just set a 10 pip stop.