a person's identity changes over time because
- the people around them
for example, the people around them might make the person more open and happy/active
- media
because the media is mostly used to influence others and by doing that the person's style/preferences change
- experience
when the person has not experienced most of the things when they were younger/in the past, they might not be very aware and they just go along with what was happening but as the experiences expand, they slowly get to realize they should be aware of this and that and as they do that they slowly become more self-conscious/ making boundaries, etc.
- mostly in social environments
most of the influencing starts there too
these are just some examples and points to help with what to write in the essay, hope this helps! :D