So what do you mean here that is a psychological effect? Well forex breakout is actually the signal of the market is trying to do something, is that either to keep the trend to the higher or lower level or changing the trend to the other direction. Remember this is not 100% working strategy, i can say at most 70%.
Yes i know it is the signal but of course that is depend on the effect of the market itself, people will look for it and make sure that they make profit from it. The one who drive the market is people based on their perception to the market, so this is why psychological effect like this forex breakout is a good signal since most people still believe it.