Science is showing us that there are neurological (brain) factors that contribute to self-control and willpower, along with learning and upbringing. And when these brain systems are functioning improperly or become damaged, normal levels of self-control and willpower are impossible.
Taking Charge of ADHD, Revised Edition: The Complete, Authoritative Guide for Parents (ed. Guilford Press, 2000) - ISBN: 9781606238424