Writing facilitates change.
Nothing facilitates change better than writing. It's a natural process to be in, and it's the very thing that makes you a writer.
One of the reasons why writing works so well for personal growth is that it has a natural facilitation effect to it.
Whenever you write, you change. It's not always a huge change, of course, but there will always be a change taking place.
For some people that's scary and for others it's godsend magic. I personally belong in the latter category and find writing one of the best tools for personal growth.
It doesn't require anything but pen and paper to facilitate whatever change you want.
In a world where constant change is inevitable, I often find it easier relating to it by sitting down and writing about it. I don't have to do anything else.