Don't give up just yet, instead of telling your supervisor you quit, why don't you explain to him/her the difficulties you are having. Maybe they are not aware that you are struggling. Maybe they are pushing you in a particular direction because it will make a stronger thesis, which will make you more likely to succeed and become a Dr. Please talk to them before quitting, I'm sure they'll do everything in their power to help you. Nobody wants you fail. Best of luck, I'll be thinking of you. FFxx