How do you forgive and forget past abuse? im 13?

well in my past years, my mom would grab me by the neck shake be, eventually let me go and walk away with an attitude. She hit me before too. But im 13 and i just cant forgive and forget. I went to this thing called a church summit tht our church does evey year and i took a cl called teen anger.well, my instructor said i have to forgive and forget(i didnt tell her nor was she directly talking to me but she said it to the whole cl). I just cant do tht. I wanna tell this one lady at my church, but i just dont have the strength and it would seem weird. plus my mom and dad are over alot of children things at our church so everytime we have a testimonial period where kids tell there life stories, they r always there.So i can never express myself and i keep things"bottled up" inside me. Now im sittin here crying because i feel so helpless. We argue like eveyday. i just want it to stop. i just cant control her. plz help