Answer: To answer this question, let's explain what personality means in this content first;
Personality is the combination of individual character, behavior, and decisions. This is always ascertain from previous records of the individual, by observing the individual behave in different circumstances.
Individual with the same record of behaviour may behave in a different way in a given occasion because our actions towards a situation is always controlled by a reactions from a previous action.
For example someone who just fought with the wife, and someone who just had a good romantic time with the wife. Even though this two has the same personality record, they actions will be very different In any given circumstances. The one that fought with the wife, is tend to behave harsh and tempered, while the one that had a romantic time with the wife, is tend to act soft and smart.