My Mom is always in my face?

My mom always gets mad at me for closing the door to my room or not wanting to go to an awards ceremony at my school. I just want her to leave me alone about these small problems. Truly I don't want to go to the awards ceremony because I would feel like an under achiever (i wasn't nominated for anything). The other thing is that I like closing my door because i would like some privacy and sometimes do like being alone. How do I express these feelings without starting an argument