Too often, the beginning trader will be overly concerned about incurring losing trades. He therefore lets losses mount, with the "hope" that the market will turn around and the loss will turn into a gain.
Almost all successful trading strategies include a disciplined procedure for cutting losses. When a trader is down on a positions, many emotions often come into play, making it difficult to cut losses at the right level. The best practice is to decide where losses will be cut before a trade is even initiated. This will assure the trader of the maximum amount he can expect to lose on the trade.
The other key element of risk control is overall account risk. In other words, a trader should know before he begins his trading endeavor how much of his account he is willing to lose before ceasing trading and re-evaluating his strategy. If you open an account with $2,000, are you willing to lose all $2,000? $1,000? As with risk control on individual trades, the most important discipline is to decide on a level and stick with it.