. "Investment professionals who spend their full-time job trying to beat the market usually can't."
An individual can't control their investments' value. No matter how consistent past returns have been, the future could always look different. While that's disconcerting for many investors, there are two things you can control: what you buy, and how long you hold onto that investment and let it ride out the ups and downs.
Malkiel writes that a group-think mentality sometimes influences investing, where people are more likely to take an action they wouldn't when a group is doing it. When people start talking about serious downs in the markets, some investors are swayed to sell off funds, and vice versa. A prime example of this type of group-think in investing was during the tech bubble of the early 2000s. "During the 12 months ending in March of 2000, more new cash flow went into equity mutual funds than during any preceding period. But while the market was reaching troughs in the falls of 2002 and 2008, individuals made significant withdrawals from their equity investments," he writes.