Related, for me, was that high school just wasn't very challenging. I got As without ever really studying or feeling that I was working very hard. I took that approach into university and it worked for my freshman and most of my sophomore courses. Then things got actually tough and I realized I could not just intuit my way through exams, and I had never really learned how to study.
Failing to realise that school was just about learning how to learn was also the main mistake I made, for the same reason as you. I was always good at soaking up stuff I found interesting, but to this day learning something because I have to is hard, awful work.
