I wrote a post a while ago about how writing really helps me express and understand abstract and seemingly incomplete ideas floating around in my head in a way that's coherent. In other words, writing helps me understand what I think if that makes sense.
Anyways here's the post where I talk a little bit more about this, hopefully you find it interesting:
https://medium.com/@iamregularguy/i-write-to-know-what-i-think-c449906cf657