How do you react when a teacher gives you lower marks for personal reasons?

It is better to disregard your feelings that the lower mark is personal; it is more useful in the long run to figure out what you needed to do to earn the higher marks. To do this, ask your fellow students if you can read their papers, talk to the teacher about the answer or qualities they were looking for in the assignment and then reevaluate your work. If it was a written assignment, making an outline of the work will tell you a lot about the difference between what you wrote and what you thought you wrote.

The higher majority of teachers bend over backwards to remove any favoritism in their grading.