I also have ADHD (Or what was called ADD before - i.e, not the hyperactive part), and got diagnosed as an adult. As a child, I was extremely hyperactive - by some mystery, my parents didn't get me examined. And since I mellowed down in my teens, them nor school bothered to do anything.
But, yes, it's awful. For me, the worst parts are:
- Uncontrollable "hyperfocus" on things you really don't have control over. It would be awesome if you could control your interest, but it's usually the other way around. Something finds you, and you can't stop focusing on it. Everything around you becomes irrelevant, it's like a drug.
- Poor time management. For some reason, things just fly by you. Because you have a hard time focusing on different things, they get neglected really fast, and you suddenly find yourself hours / days / weeks later, remembering that you should have done some thing. Taking out the trash, paying your bills, handing in homework, getting your car looked at, etc.
- Having a hard time reading long pieces of text. During college I absolutely loathed classes with a lot of reading, as I'd read the same part 4 times over, zoning out each time.
- Zero sympathy from other people. You easily get branded lazy. My teachers said year after year that I was bright, but lazy - so I figured there's nothing wrong with me, I'm just lazy.
- Depression and anxiety etc. that comes and goes. I especially remember back in college when I studied Engineering, and most of my classmates would study 12 hours a day, deep into the books. It was impossible for me to do the same, so I pretty much lived from one all-nighter to another, feeling like a total fraud because I couldn't dedicate 1/10th of the time to school, as my buddies did. My anxiety was over the top.