One of the greatest advantages of trader has when in the Forex markets is a high degree of volume in the markets. This is highly advantageous because it helps ensure of fill for every single trade. With lower volume markets, you are likely to be spending a lot of time arguing with your broker and having to deal with the failure to fill a particular trade. The Forex volume levels do not allow for this. This is one of many advantages that comes from trading on such a liquid market.
The reason this happens is quite simple. The Forex market is so incredibly large and has so many people trading at any given time that any person can buy or sell any currency pair without having to worry about getting a trade on the other end. This means that traders can focus solely on working with technical analysis and market analysis to figure out their trades without having to wonder if the broker is going to hold a trade for them. The Forex volume levels give a greater degree of freedom when trading.
Not only this, but on pairs that have an extremely high volumes such as the EUR/USD, you'll notice that some brokers will have so many trades going on at one given time that they can actually afford to lower their spread. This means that if you are trading a very high-volume pair, you are likely to get more profits and more money from your Forex trading. This is just an example of how the Forex volume levels can affect trading.
However, when there is a reason announcement that affects the market in one particular way, there is often such a dramatic spike in volume that the brokers find it difficult to fill all the orders. This is often because there are too many people buying and not enough selling a particular currency. When this happens, spreads are likely to increase because the chances of getting a fill become much smaller since getting a fill for trade becomes much more difficult.