While this is just common sense, ignorance of the principle, or carelessness in its employment has caused disasters to many traders in the course of history. Nobody knows where a currency pair will be heading during the next few hours, days, or even weeks. There are lots of educated guesses, but no knowledge of where the price will be a short while later. Thus, the only certain value about trading is now. Nothing much can be said about the future. Consequently, there can be no point in adding to a losing position, unless you love gambling. A position in the red can be allowed to survive on its own in accordance with the initial plan, but adding to it can never be an advisable practice.