Despite being able to trade 24 hours a day, 5 days a week, you shouldn’t (Forex trading is not quite 24.7). You should only trade a forex pair when it’s active, and when you’ve got enough volume. Trading forex at weekends will see small volume. Take GBP/USD for example, there are specific hours where you have enough volatility to create profits that are likely to negate the bid price spread and commission costs.
Many new traders choose not to close a trade because the market is still moving in the direction they want it to, only to then lose all of their gains when the direction suddenly changes. If your trade hits your predetermined target, close it and enjoy your winnings. If the market moves in the opposite direction, close the trade or set a stop loss so it will close automatically.
When you're making trades in the forex market, you're basically buying or selling the currency of a particular country. But there's no physical exchange of money from one hand to another. That's contrary to what happens at a foreign exchange kiosk—think of a tourist visiting Times Square in New York City from Japan. He may be converting his (physical) yen to actual U.S. dollar cash (and may be charged a commission fee to do so) so he can spend his money while he's traveling.
The mere expectation or rumor of a central bank foreign exchange intervention might be enough to stabilize the currency. However, aggressive intervention might be used several times each year in countries with a dirty float currency regime. Central banks do not always achieve their objectives. The combined resources of the market can easily overwhelm any central bank. Several scenarios of this nature were seen in the 1992–93 European Exchange Rate Mechanism collapse, and in more recent times in Asia.