This Trading Strategy is the most important and you should decide the specific points when to open your trade and close your trade before entering into it. These opening and closing points in your specific trade should be decided well before placing your trade order.
You can change your decisions according to the market movements periodically, but you should fix how much money you can afford to lose in each trade and close your trade while reaching that point. If you go beyond this limit thinking that the market will move positively to give you more profits, it may end in incredible losses which you must have not thought of where there are chances to lose all your investment.
Taking such kinds of risks in trading is not a rational decision and is done due to Emotional urges. Emotions should be completely avoided in trading and the decision-making in Trading should be purely done on a Rational basis.
Clear decisions on entry and exit are more important in Day trading and Scalping as the trading time is less and more skills are needed. In Position trading/Investing and Swing trading, you have some time to make decisions on closing your trade once you open your position.