That everything in life is a choice.
i.e: Being the best and most extraordinary student is very attainable, it's an active choice to be the best and study the hardest.
For most my life, I thought that I just "wasn't a maths person" and that "I'm not smart enough for xyz".
But then somewhere along the way I realized that being great at something is a choice, you yourself choose how you want to allocate time and training.
Once I finally figured this out, it was as if all the things that I previously had thought to be magic, turned out to be very achievable.