When people ask me to share the most important thing I learned in college, I always have to say, "We're going for optimization, not perfection."
This is hard for me to come to terms with.
a life-changing book
Grades aren't a measure of how much you've learned. You can get perfect scores on everything while learning nothing. You could also learn more than you've ever learned in your life while failing every test. The important thing isn't the grade: it's that you improve every day.