As someone with ADHD, the author’s issues sound very much like ADHD. I have yet to hear of someone who has a “lack of discipline” to this degree who does not have ADHD. I used quotes because the concept of discipline is also very relative.

I have yet to hear of anyone being told by a medical professional that they don’t have ADHD but instead simply lack self-discipline. Yet probably many people become depressed or feel hopeless because of comments like this.