Before jumping on placing any position, you should create an idea about how much can you afford to lose and when you should implement your exit strategy, especially your downside risk.
So, you should strictly decide with yourself where the point of pain stands, so you cut any order outside this limit, in order to keep your trading account safe and healthy. Constantly allowing losing trades to go beyond this point is a recipe for failure.
Another habit of successful traders involves defining the size of the positions. For every trade you open, you should decide on the size of this position, according to the size of your account. This can help you keep risk under control.
Another good habit of successful traders is not rushing to trade. Trading decisions should be well though and considered carefully. This means, a trading plan should be prepared in advanced and you should stick to that plan. Do not open trades based on your emotions of excitement, greed, or fear. Do not act randomly. Act mindfully. There should always be rational reasons for getting into and out of market positions. The fact that a market is rapidly moving in one direction or another may not constitute a rational reason for getting into a trade.