In episode 6, Lee and Carrie chat about one of the big five personality traits, neuroticism (which is sensitivity to negative emotion). 

One's level of neuroticism, like any other personality trait, can be better described as falling somewhere on a sliding scale. For example, Carrie is generally higher in neuroticism, as she tends to feel negative emotion more intensely than the majority of people. 

You'll also hear how this isn't always a bad thing, how Lee and Carrie are similar when it comes to neuroticism, how they differ in the trait, and how understanding it has contributed to their marriage growth.