It is true that no one can always accurately predict the future in currency market. If someone could do it he would quickly become the owner of all the money in world. However you do not need to predict the future to successfully trade in the market. For example the most successful investors like Warren Buffet do not predict the market. What they interested is to increase their investments in the companies that give them highest return. They are not interested in crystal ball of market prediction.
Market predicts and defines itself. We as traders do not need to predict its movement. All we need to do is to synchronize our actions with the market movements. We need a trading method to do that. For example we need a method that allows us to define the current trend. Such a method should harmonize us with the market. The whole idea of predicting the market is closely related to the idea of having control over the market. It's a typical utopian idea to predict to be able to control. This approach is fatal for trader's psychology. Such trader will blame the market because it moved into a wrong direction then he has predicted. It's the source of losses for most trades.
Most traders think that the main reason to succeed in trading is the ability to predict the market. They will suffer because they think that they know better what market should do. I think that a good trading strategy does not have to predict and control anything in market. That means it should exclude emotions of trader from the decision making process completely and leave him only the opportunity to act by executing trades.
I know such systems exist. The difference of these systems from the ones that based on predictions is that they have already incorporated losses in themselves that are related to lagging indicators. The only problem with those systems is that thy may not be as profitable as the systems based on traders discretion. But until you learn to make profit with such mechanical system you will not be able to control your emotions to make profit with discretional systems.