Is There a Hard Lesson That Will Make You Better in Your Career?

This was always my problem with school. It was i couldn't apply it to anything. So as always like, oh ye, i got to take calk three. How does it supply to real life? And stuff like that. But this kind of disconnect of the theoretical verses practical is what drove me to be a better engineer. I would sit home and i would code in my free time, because i was always like, what can i do? Is this possible? What about this thing?"