Your personality, basically a word to describe your habitual behaviours, is believed to be formed as a result of both nature (neurological development) and nature ( the environment you grew up in)

In general the foundation of your personality, based on nature and nurture, is believed to be set by your early teens.  Your habitual behaviours can change over time but like habits in general, it is usually slow and difficult to do.

Maturity

Maturity decribes growth and advancement in your behaviour.  This is largely based on experience.  The behavioural changes you make as time goes by and you gain maturity can include impacts to your habitual behaviours (personality).

The way a person might typically behave in given situations have been studied and labled as personality types.  The level of conformity, efficiency and effectiveness of overall behaviour is typically used to gauge ones maturity.

While typically personality is considered set at a young age, as you grow older and mature in other behaviors so can your personality mellow and mature.  Personality and maturity can combine to create change.

Continuous Improvement

The point is, although your personality can be an underlying defining aspect of your core behaviour, as you mature it can and will change.  Continuous improvement of your overall behaviour is not only possible, it is desirable.

To coin an old television conmercial for a ladies cosmetic product, your not getting older, your getting better.  Don’t ever give up improving your behaviors, both those you interact with and those you will be interacting with, salute you for continual striving to behave better.