I learned how to fail and learned how to recover from that.
My first two years of uni were like school, an absolute breeze. I aced all my classes, made friends easily and had a tonne of extra-curriculars. Then third year of Law School hit and all of a sudden it was 10 times harder, 20 times more competitive and we really had to focus and study super hard...and I failed my first class. That was super demoralising for me, I'd never failed a test in my life let alone an entire paper. I swear I cried for like two days.
My mum was the one who said, ok now welcome to the real world. Everyone fails things, you just have to pick yourself up, learn from what you did wrong and try again.
Looked at where I went wrong, took the class again, passed it, and moved on.
The world didn't end because I failed something. Pretty important lesson for me.