Let's say you are a bull, and the Fed is tightening, corporate earnings are sputtering, the yield curve is inverting. Do you drive straight through the red light, going aggressively long the Nasdaq-100 Trust ( QQQQ)? Or do you notice the signal? Now imagine you're a bear and sentiment is at an extreme negative, year-over-year S&P 500 earnings have gone from bad to so-so, and the Fed is cutting rates. Do you stop at the light, shorting the Spyders ( SPY), even though it's bright green? Savvy investors get long or short (or move to cash), as conditions dictate. When all the signals line up in the market's favor (regardless of style (valuations, sentiment, monetary policy, etc.), the smart investor gets long. When the indicators line up the opposite way, that investor gets defensive. The terms bull and bear are anathemas to me. You can be long or short or mostly cash at various times -- sometimes all at the same time. So why commit to dogma? The market does not require you to declare your party affiliation or sign up for a religion. "Are you now, or have you ever been, a bear?" is not a question on a new account form. If there's a perceived advantage to being bearish, you should get bearish and vice versa. Now, on to the public's reaction to bearish or bullish calls: One of the typical emails I get, particularly after making a bearish argument is: "In the long run, doesn't the market tend to go up? Isn't that reason enough for a bullish bias?" It depends. If you bought stocks in 1966 when the Dow first hit 1000, well, the long run hardly bailed you out. The Dow didn't get over 1000 until 1982. How'd you like to spend 16 years and end up with a precisely 0% annual return? And that's before factoring in inflation. The problem with the so-called long run is that it overlooks the here and now. "This long run is a misleading guide to current affairs," wrote John Maynard Keynes in his seminal 1923 work, A Tract on Monetary Reform. "In the long run," Keynes noted, "we are all dead." It has also been an excuse for some terrible advice. Example: "Buy and Hold" works well during some periods (1982-2000) and poorly during others (1966-1982; 2000-2005). If you noticed a pattern here, you are already ahead of the herd. Adaptability is the key to surviving these longer-term cycles of boom and bust. It is important to have a degree of sensitivity to changing market and economic conditions. Once you recognize a transition is taking place, or hear someone who does, you must be flexible in your response. It's a lot like Darwinian evolution: Adaptability remains the key to survival. This is just as true for investors as it is for iguanas. Ignore the market's reality in favor of the long-term view, and you'll die with your conviction intact -- but likely little else.