Contrary to popular belief, it is known today that personality, empathy and intelligence do evolve over our lifetime. Although it is easier when we are younger, we can still learn, adapt and evolve whenever we want.
Our brain doesn't stop evolving and develops according to our needs when we "ask it to". The brain isn't limited by age, new neurones and new neural padrones (or new knowledges and skills) can always be created - life is changing and being alive requires change.
The longest study about human personality couldn't find significant similarities between the 14 year old and 77 year old self of study subjects. The study conducted by researchers from the University of Edinburgh indicates that our adolescent personality can be very different from our personality in late adulthood.
The study began in Scotland in 1950, when 1,208 14 year olds answered a personality assessment questionnaire in order to evaluate their self-confidence, perseverance, emotional stability, ponderation/ scrupulousness, originality and willingness to learn new things. In 2012, 635 of the 1950's adolescents were successfully located and now 77 years old, two-hundred accepted to participate in a follow-up study which showed that there wasn't a significant statistical relationship between the 1950's results and how they themselves, their relatives and their friends classified the participants' personalities.
The study isn't conclusive as it doesn't determine that this necessarily happens to everyone but rather indicates the possibility that our personality can change over our lifetime. These results agree with those of other studies which suggest that the longer the time frame between questionnaires, the bigger the differences between who we were and who we are today. Haven't we felt this? Especially when we look at an old picture taken decades ago when we were just five or six years old... Is it us? Or is it someone that we once were but is gone now in favour of a different (better) person? Like a river that flows in the same place forever while constantly receiving new streams of water.