Life experiences can also include events that have a direct physical effect on the prain.  Encephalitis, a head injury, drug or alcohol abuse can lead to brain changes which, in turn, affects personality, particularly if this occurs at a young age.  Brain injury in young and old alike can lead to profound personality changes and the term Post Head Trauma Syndrome is often used in such caes.  Personality continues to be shaped and hanged throughout adult life but this is subtler as we get older.

Personality then, is the sum total of all the above - heredity, parenting, and life experiences.  It shapes and makes us the way we are - each unique and different, although sharing many features in common.

Personality is the lifelong and enduring manner in which an individual greets, interacts, and deals with the world around them.

Personality disorders evolve much the same way as normal personality develops, however, in some it may be a major effect of heredity, in others the influence of negative parenting and negative early life experiences may play a major role.

It is non-productive to think of one's personality as "disordered". Rather, one should be aware that aspects of one's personality can create conflict and this needs to be changed.  As with all personalities, there are strengths and weaknesses, good points and bad.  We need to search for and recognize our strengths while we seek to change our weaknesses.