For every trade you enter you should have a plan, its the lifeblood of a trader. There are only two ways a position will stop out if you have a valid criteria to enter in the first place. First there was some sort of market change that effected the setup. There is nothing you can do about that, and unless it starts to happen with great consistancy its not something you can worry about. The next reason you can stop out, or just simply underperform, is by not following this plan. This is where traders go broke, even if they have a valid approach. If you are not following your plan, then there is some reason for this and you need to find out what it is and kill it before it kills your account.
Brandon