It is simply not possible for any trader--whether amateur, professional or anywhere in between--to avoid every single loss. The disciplined trader is fully cognizant of the inevitability of losing hard-earned profits and, as such, is able to accept losses without emotional upheaval. At the same time, however, there are systematic methods by which you can ensure that losses are kept to a minimum.
Every trader should employ a loss-limit system whereby he or she limits losses to a fixed percentage of assets, or a fixed percentage loss from capital employed in a single trade. Think of such a system as a circuit breaker, or collar, on the trade. After a certain percentage has been lost from his or her trading account or principal traded, the trader may very well stop trading entirely or may immediately exit the losing position. With this system, exiting a losing position is a single, unemotional decision that is not affected by any hopes that "the market is sure to turn around any minute now."