Growing up is a part of life.
Yes you do grow up but forcing it does not help either. There is no reason to change who you are just for the sake of being mature.
Change rarely happens because you want it. It's just something that happens to you as you grow older and experience all kinds of things throughout life, both positive and negative. And some people have no choice but to change themselves.
Oh there are plenty of people (teens) who just want to be "mature" and force it.
I agree with fipse, if people change when they don't want to then the change is pointless. change could be a conscious decision or it could be unconscious, but the important thing is that you don't force it.
and when you say "change rarely happens because you want it" I imagine you are talking about outside/uncontrollable factors, the change me and fipse are talking about is your reaction to those factors. you can control your reaction, and your reaction should be something you are comfortable with
you grow as a person when you look at a situation and say "hey, I was wrong" not when you look at a situation and say "hey, the world thinks I am wrong". the latter reasoning is stupid and harmful.