Why is good to have a planner if you have ADD, and use it every day?

I'm participating in an ADHD research by University of Zürich. It is 2.5 year long, I have to go in this time 5 times to a test, and I have to fill out plenty of surveys.
The first year is over. I started to use planner(s) in this year, and learned a lot about time management, organizing, and also about ADD. Things are going even better! I was today in the Brain Assessment Research Center, where the research leader told me, what changed in my brain. Lot things! Concentration is better, emotional stress is lower, different areas in my brain working better together, the excessive reaction on tones went back to normal. He asked me, what I did? Because what happened with my brain is amazing. I told him about my journey in planner land, show him my Filofax. He was very impressed me, he told me, I should teach him :D
I never thought, that my brain will also change. I used planning only to make my life simpler. But it is changed me too!