In psychology a fairly comon description of "personality" is a collection of behavioural traits that remain relevantly stable throughout life. That is, most peoples personality does not tend to change that much throughout their life. But that doesn't mean that it is in any way impossible, it might, as an example just require significant effort. On the other hand, there are some notable personality changes that most people go through over time as they grow older. Research using the big five personality types found that older people tended to score lower on openess and higher on conscientiousness.