Hello. i am a 23 year old girl. engineer by qualification. considered bright by all around me. now preparing for a difficult service exam in which i have failed in my first attempt. im under a lot of mental stress in my second try now. i hardly get chances to talk with my best frens since all are busy with their jobs. My problem is i get very angry when my mom hums or sings songs. she is a bad singer. im not a great one either. But i realised that my anger and shouting was abnormal when one of my friends shockingly pointed out and said she has never seen this side of me. I was embarassed. Help. Am i fighting psychological problem?

Summarized question: Under stress. Preparing for exam. Getting angry. Suggestions?