Absolutely not! Although turbulence has been known to cause injuries and affect airplanes, the instances of it are too rare to worry about. Apparently over 25 million Americans (as seen in Newsweek Magazine) are afraid to fly and turbulence is the #1 fear. ALL air is disturbed to some degree, although often it's so minimal it feels like smooth air to us. Most rough air is simply the equivalent of driving over a rough patch of road or of steering a boat through rough waters.  There are different causes of turbulence, like hot air rising over the desert, convective turbulence (the kind you feel near thunderstorms), etc.  In over three decades of flying I have NEVER been adversely affected by turbulence other than just annoyed by it.  Flyers experience it to some degree virtually every time they fly and I equate it literally to the fact that if you drive for any length, you're bound to hit a bump or two.