During my apprenticeship I had to file copies of sent bills. Once sorted by number and once sorted by client an number. I was slow, made lot of errors and I had headaches every time I had to do this, two times a week. I got problems because of that, nearly lost the job. And the worst part: they didn't let me do the interesting tasks until I'm able to do the "easy" things right...

Nobody thought that maybe it's ADHD. Got diagnosed 25 years later...