I am an adult with ADHD, possibly with Asperger's syndrome. I can relate to your experience with regards to knowing that you could complete a task but didn't. It's so sad and frustrating to see so much unfinished projects. I also hate medications, since they don't work for everyone, and in my case they made me depressive.
Strangely, I am a fast reader and a fast learner, but when in comes to everyday life I can be very inattentive, mainly because I don't find it as interesting as college and the subject I study.