Try to think of the aeroplane as nothing more than a really big car. Turbulence is often nothing more than the quivalent of driving along a bumpy road, with the occassional pothole to give a bigger bump.
It's uncomfortable, and frankly a bloody nuisance, but cars and planes cope with that sort of ride no problem at all.
Then you have the more turbulent conditions associated with jetstreams and large storm cells. Very unpleasant, and from a piloting point of view, probably the equivalent of driving very fast down a rough farm track.
Not something you would choose to do, and something all pilots avoid if we possibly can.
However, again comparing it to cars, if you watch the beating that rally cars take you just wouldn't expect them to hold together, but they do. Aeroplanes are no different.
Don't worry so much, and try to enjoy the good things that flying brings.
PS. Hosties are always fun to watch with a little jiggling!
