Cycling...................

 The way I see it there are really only two constants in the markets: risk and cycles.

Risk has to exist because without it there would be no reward.

And nothing is more dependable than cycles because market psychology, fundamentals, risk appetite and investor emotions are constantly changing. Strategies, asset classes and securities go in and out of style in part because the pendulum always swings back and forth between fear and greed but also because the future is unknowable.

-Ben Carlson, from here