Any experienced trader can tell you that his greatest losses have been taken on those rare occasions where he substituted stubbornness for a proper stop loss technique.
The proper way to trade is to establish where a stop loss will be taken before the trade is made. I recommend risking an initial fixed amount because it simplifies calculations and order entry. (In other words, you don’t have to think about it too much!).
You can then pull the stop up tighter if the trade does start working in your favor. If a trader waits until he has a loss before making that initial decision, his judgment is almost certain to be affected.