Parents are annoying

My mom is so annoying. I mean it is the end of the school year and she is still yelling at me about grades and all that. I am trying my best to get A's but she still pushes me. That puts me under a lot of stress and makes me get very annoyed with everything she says. Sometimes I want to yell at her to shut up since her voice sometimes annoys me. How is that even possible?
Just today she was yelling at me since I was getting annoyed wiht her again. I cant even say I am sorry now since she left for my little sisters baseball game.
My mom wonders why I keep my big mouth shut and this is why, because I am afraid that my voice and mouth will betray me and make me say things that I dont want. So now I feel like I have lost my voice and so does she. But it was my chose to and I am sort of happy about it. But also sad since my mom hardly talk to me anymore. But what can you do about if since you feel like your mouth is going to betray you and your afraid of what you might say.