Trading is a tough job — emotions can run high when things are moving our way, let alone when things are not moving as we want. A series of losses can make you abandon your trading plan and start trading haphazardly, which will even lead to more losses.
So, to maintain low-risk trading, you must have a maximum number and dollar amount of daily (if you are a day trader or scalper), weekly, and monthly losses beyond which you suspend trading for that day, week, or month.
After a series of losses or a huge single loss, it is advisable to avoid trading and do something that will help you clear your mind and regain your emotional capital. When you are coming back to the market, start with demo-trading to build your confidence.
Many of the best traders will walk away from the screen once they have lost or achieved a certain amount of points in one trading day. This is a very disciplined practice and can keep your account at a very safe, stable growth-rate.