In one of my college math classes, the day after an exam, the professor had this quote already written in a small corner of the board at the beginning of class:
It is not Justice — the servant of men, but accident, hazard, Fortune — the ally of patient Time — that holds an even and scrupulous balance. -Lord Jim
And we stared at it, off and on, during class. Finally, at the end of class he made a few remarks about the exam, and ended say that if we were unhappy with our scores, we could be comforted by the words of Lord Jim.
I think the quote means that in human dealings, "fairness" is a concept both hard to define and hard to achieve. There are just too many variables. But it evens out over time. Don't sweat the small stuff. Luck may have given you an easy exam today. Next semester, you may work just as hard on a subject and get an especially hard exam. That exam is just one part of your course grade, your course grade is just one part of your overall college rank for the semester and at graduation. And the importance of your college rank fades more and more as you get a job and get older.
Take the grade and move on.