Buy the winner sell the loser: bone or bane?

As a new investor, this is a common mistake to buy a winning stock and sell a losing one often resulted in buying high and selling low. It is misguided by greed and fear (emotional trading). 🤑😱
We should DYODD before investing in a stock - buy the stock because of the company fundamental and not just based on the share price. Hence I always remind myself to follow some investment rules:
1. Set up an investment objective. Have an exit strategy for short or long run. Either sets a stop-loss order for a decline of 3% to reduce any big losses or apply a thinking framework to help you decide whether to sell.
2. Before any portfolio change, ask yourself these questions:
Why did you buy the stock?
What changed?
Does that change affect your reasons for investing in the company?
3. Once a stock has been identified, apply DCA to avoid emotional buying and selling.
4. Understand the psychology of money such as setting up emergency fund, be frugal in spending etc. This is to ensure that you have the holding power.