What about pomodoro technique. I have mild adhd and I have seen great results to just follow the rule of the pomodoro ( focus for 25 minutes and a daily TODO list) super simple but I have seen great results. It has improved my work and happiness. When I was a child/adult under education system I used these medications and they had a great effect I could concentrate on something and be interested for longer times, I passed from average to one of the best in class. I wonder if Id used the pomodoro technique instead I would had felt the same, could this be solved with just discipline.