From Howard Marks:
There are two things I would never say when referring to the market: "get out" and "it’s time." I’m not that smart, and I’m never that sure. The media like to hear people say "get in" or "get out," but most of the time the correct action is somewhere in between. Investing is not black or white, in or out, risky or safe. The key word is "calibrate." The amount you have invested, your allocation of capital among the various possibilities, and the riskiness of the things you own all should be calibrated along a continuum that runs from aggressive to defensive.