What is the most unfair thing in life?

Sometimes we feel that life is unfair to us. I met with such an incident recently. We had Internal examinations in my B.tech 4th year, Ist semester. Very unlike me, I have attended all the classes of "Mechanics of Solids" paper because seniors said you have to pass the subject in one go. You cannot afford to fail in the paper as it will be difficult to cope up.

My friend Tejas has not attended even a single class. On the day before the exam, he came running to me and requested me to teach him at least some important topics. I accepted because that will be a revision for me also. We studied until the late night that day and went to write the exam in the morning. I wrote well to my satisfaction and Tejas also said he wrote well and thanked me a hundred times that I have taught him the entire subject in one day.

When we checked the results, both of us got 16 out 20 in that subject. Tejas was jumping with joy and I understood what do you mean by "life is the most unfair thing".