I came across this quote on the excellent website Understood.org: 
Nelson J. Dorta, Ph.D., is a pediatric neuropsychologist in private practice in New York City as well as an assistant professor of clinical psychology in child psychiatry at Columbia University College of Physicians and Surgeons. This metaphor captures how harmful this “just try harder” attitude can be when trying to help students with ADHD. Because ADHD is an invisible learning difference, many people—including well-meaning professionals—can sometimes fall into the trap of thinking that if students just “work harder” or “concentrate more” they can will themselves into overcoming their struggles. To take the metaphor even further, I would consider executive function strategies to be the “glasses” for these students, allowing them to approach their work systematically and with the overall goal in mind. So the next time you’re having trouble explaining why someone with ADHD can’t simply make themselves focus, consider sharing this quote!
- Elizabeth Ross, M.A., SMARTS Media Manager