I can focus on my work all day with no medication if I'm doing something that I find personally interesting. However, when I have a week's worth of online coursework and boring bookkeeping to do it's impossible to get more than 5 minutes done without staring out the window, putting something on in the background, and twiddling my thumbs. I can still buckle down and get work done without it, but it's so much more mentally draining to do a week of work without any medication than if I were just to take what the doctor recommends. YMMV obviously, I just wanted to suggest something for people like me who have been 'proudly' living with ADHD un-medicated.