Loosing money in forex is the part of the game. Don't let it freak you out, however it doen't mean you can be careless. Loosing money and learning from mistakes is one thing.
Careless trading is another story. If you aren't careful, your account funds can fall below the available amount (which is called Margin Call). When this happens, your forex broker has every right to shut down some or even all open positions to stop your account from getting into negative balance. A good thing about it that you will never lose more money than you actually have. The bad thing is that Margin Call are evil and here is why.
Stay away from Margin Calls by monitoring your trading activities and margin balance. Set stop/loss orders on your positions and minimize the risk of loss. There are many tools to help you out with almost all trading platforms we have reviewed over the years.
If you do trade on margin account make sure to be very clear about the broker's policies and all those conditions written in very tiny font. The last thing you need is to get into trouble. For example, during the weekend the margin can raise from 1% to 2 or even higher.