Recently, a friend asked me about stop-losses, and I realized that many novice investors actually don't have a thorough understanding of this concept. To put it simply, a stop-loss is when you decisively exit a position once the loss reaches a certain level, preventing the loss from continuing to grow.

In my years of investing experience, the most profound lesson I've learned is the importance of timely stop-losses. For example, suppose you buy Apple stock with 10 million USD, and later the stock price drops 50%, from 100 USD to 50 USD, your capital becomes 5 million USD. At this point, many people might think, "I've already lost, so I might as well wait and see if I can break even." But in reality, to go from 50 USD back to 100 USD, the stock needs to rise 200%, and psychologically, you've already been hit hard, making it very easy to accept a loss and sell when the price drops further, resulting in a loss exceeding 50%.

Conversely, if you had set a stop-loss at a 10% loss, your remaining 9 million USD would only need an 11% gain to recover the loss. The benefits of this approach are obvious. The core meaning of a stop-loss is: first, to prevent losses from expanding further; second, to improve capital efficiency.

So why set a stop-loss point? There are several reasons. First, sometimes our reasons for buying stocks might be completely wrong, and a stop-loss helps us correct these mistakes in time. Second, market conditions change rapidly; what was a valid reason yesterday might no longer hold due to environmental changes. Additionally, during market panic or irrational sell-offs, setting a stop-loss allows us to avoid risks promptly. From a technical perspective, if a stock breaks below an important support level, it often continues to decline, and without a stop-loss, losses can escalate quickly.

Regarding how to set a stop-loss point, there are many methods. The simplest is to set a percentage or dollar amount of loss, such as a 10% loss or a $100 loss. If you want to be more precise, you can combine technical indicators. For example, look at resistance levels; when the price repeatedly hits a certain level but cannot break through, that can be set as a stop-loss point. The MACD death cross is also a good sell signal. Bollinger Bands can be used too; when the price falls below the middle band from the upper band, it’s a sell signal. RSI exceeding 70 indicates overbought, below 30 indicates oversold—these levels can also serve as stop-loss references.

In practical trading, there are three ways to implement stop-losses. The first is manual stop-loss, where you close the position yourself. The second is conditional stop-loss, where you set a price point and the system automatically executes the sell, so you don’t have to watch constantly. The third is trailing stop-loss, which adjusts automatically as the price moves, especially suitable for those wanting to maximize profit protection.

Honestly, many novice investors lose heavily mainly because they haven't established a proper risk management mindset. Setting and executing stop-losses promptly can often save you at critical moments. Now, no matter how optimistic I am about a target, the first thing I do is decide where my stop-loss will be—that way, I feel more at ease.