Interpersonal Normality
Most definitions of normality consider interpersonal normality, the comparison between many different individual's behaviours to distinguish normality from abnormality. Intrapersonal normality looks at what is normal behaviour for one particular person (consistency within a person) and would be expected to vary person-to-person. A mathematical model of normality could still be used for intrapersonal normality, by taking a sample of many different occurrences of behaviour from one person over time. Also like interpersonal normality, intrapersonal normality may change over time, due to changes in the individual as they age and due to changes in society (since society's view of normality influences individual peoples' behaviour).
It is most comfortable for people to engage in behaviour which conforms to their own personal habitual norms. When things go wrong, people are more likely to attribute the negative outcome on any abnormal behaviour leading up to the mishap. After a car crash, people may say "if only I didn't leave work early", blaming the crash on their actions which were not normal. This counterfactual thinking particularly associates abnormal behaviour with negative outcomes.
Read more about this topic: Normality (behavior)