Exam Week... kill me!

I am 15 years old and for 2 years now I have been learning and studying for the igcses. It kind of crazy to think that for two years knowledge you only have few hours to write it in a paper. I dont believe this is the way you show someone if you have learned or not.. what if is an really bad day for you? People should not judge your grades but yes your effort. I am dedicated I no that, but usually in tests I get nervous and the results are never perfect.. wish I could be different in this kind of aspect, but I am not.. so, wish me luck guys, I really need it :)