Kathy: In our Moneyball investing methodology, we only pick stocks that are sound when we invest in them. If the stock price of the company we choose does fall considerably, it is almost always due to a general black swan event or from negative sentiment surrounding the company. The important thing is that it is not due to a change in the fundamentals of the company and that the problems are likely to be solvable. And when it is such a situation, we will continue to hold or add to our positions. As investors, you must have the kind of conviction where if you can like a stock at $100, you must be able to love it at $70 and have no qualms about buying more at a lower price.
Investors must understand that in the short term the stock price has nothing to do with the company. The stock market is a voting machine in the short term and in the long time a weighing machine. In the short term the stock prices are either driven by the intentions of the market makers or by the emotions of the market.
Hazelle: Many investors sell when the prices drop too much partly because some of them put in stop losses. Because that is what is commonly advocated in financial media or investing books. How stop losses can be used to help to protect us are too sweet sounding. But in practice, the truth is stop losses hardly accomplish what they are meant to. Stop losses force you to choose an arbitrary figure where you cut losses, say if a stock falls more than 10%, 20% or 30% which happens more often than you think. And it is not necessarily that because there is an issue with the stock you pick but rather part and parcel of the sentiments-driven market cycle.
Hence for investors who use stop losses, they will often have their stop losses hit. They will take in the losses and the next thing before they know it, the market miraculously recovers shortly after that.
The best defense for stocks investing is not having stop losses. But rather, to actually understand how the stock market works, understand how the big boys affect the stock markets and to have a basic grasp of fundamental and technical analysis. In addition, one can mitigate his risk with asset allocation and position sizing instead. Stop losses are only needed for example if you do trading where you need to predefine your profit target and where you cut loss.