You should never make investing decisions based on what the market is doing, except for now, maybe.
Past experience and reams of studies tell us there is no way to time the market and that we should buy and hold. That said, there are a few exceptions to the rule. With the total United States stock market up nearly 200 percent from the 2009 lows and increasing worries about what some pundits are calling “bubblelike valuations,” there are a few reasons you should think about selling now.
Read the rest of the article on nytimes.com.