Don't worry about turbulence in terms of the safety of the aircraft itself. As cblaisd pointed out the aircraft are significantly over-engineered and can survive much worse turbulence then is ever experienced in-flight, especially since modern weather radars have made it much easier for pilots to avoid much of the bad weather in the first place. And when they do decide to fly around weather cells, it's primarily for the comfort of the passengers rather than safety.

The only real danger from turbulence is inside the airplane, from people and objects being tossed around the cabin. Even that is pretty rare, but that's why the airlines tell you to keep your seatbelt fastened even when seated. If you're buckled in, your chance of injury of any kind of turbulence is very low.