Complex sentence: Jarrett was best known for his calm demeanor, and he became known as "Gentleman Ned Jarrett", yet he was an intense competitor when he put his two hands on the steering wheel of a NASCAR Grand National stock car.
Split into simpler sentences: Jarrett was best known for his calm demeanor, and he became known as "Gentleman Ned Jarrett". Yet he was an intense competitor when he put his two hands on the steering wheel of a NASCAR Grand National stock car.