I once had a talented, highly accomplished friend who, a few minutes after asserting something, would say, "I never said that." Similarly, some children often deny responsibility for a misdeed despite evidence being apparent. In adults, this behavior has become understood in recent years as a selective impulsivity in an otherwise well-controlled person, they exhibiting such behavior only in selective areas of their life.
This usually reflects not an impulsive personality but contradictory impulses in particular areas of ife, perhaps those related to self-assertion or intimacy. As example, the person who is repeatedly sexually seductive only to quickly reject their partner to seek another "conquest." Another example is the person who lies impulsively but states lying is not a problem for them and accuses others of lying. These behaviors are emotionally disconnected from each other, being the essence of what is termed "compartmentalization."
The unconscious is very powerful and one must respect its power.