For me it was hiding my emotions while dying of anxiety inside. I thought it was normal for people to have multiple streams of thought at once and to wake up with your mind immediately racing til bed. I did it though, college, kids, house, corporate IT career, until I couldn't handle the grind of daily life and burned out hardcore, several times. Also drank excessively for 20 years.
Thankfully, you can get treated for depression and anxiety for decades, then spend thousands of dollars to get an official ADHD diagnosis, maybe. And the stimulants make my anxiety and depression so much better, and they are super easy to get. Also, no one will question if you really have ADHD, support all the way. Then, back to the grind which you'll run right into with a smile everyday. I love it! It's the best!