Forex markets are volatile, and it is common for portfolios to get wiped out within seconds due to currency fluctuations.
Things will get more complicated when the position is taken using leverage. It may improve profits, but it also magnifies any loss. Added to all of this, a retail trader just does not have the information access that a financial institution has.
All these factors make the odds of making consistent profits slim. Having said that, with right knowledge and experience one can learn to navigate the perils associated with Forex & CFD trading.