You're right, there is a difference between not being able to maintain focus and getting bored easily. Though that is often difficult to discern when you're in the middle of dealing with it. I'm also a motivated self-teacher, but ADD gets in the way of my motivation and focus, and at times makes it difficult for me to finish or work on the things that I want to get done.

I don't know if you're arguing with what I said, or if you thought I was criticizing the author, which I'm not. I saw two keywords and for me they line up with a list of symptoms which I know can be quite troubling if you think you are to blame for being lazy or not able to accomplish the things you want in life because you keep getting in your own way. It's a difficult nut to crack, but if you think you might also suffer from ADD, it's wise to research it and speak to someone who can offer a diagnosis and help you find a solution that works for you.