<human>: Provide a brief overview of the text.

I was sleeping and my partner started thrashing around in bed and then I realized he was punching my arm, hard. He was awake. He didn't say anything when I asked him why he punched me. I was shaking a lot and I started crying. He didn't apologize or anything. He said he was suddenly angry and punching the bed. My arm had a huge black bruise on it for almost 2 weeks with a lump under it. 

I was just sleeping. I think it's sick and twisted what he did to me. I don't know how to leave without him freaking out and hurting me or trashing our apartment. Please help me with some advice. He seems to have calmed down and now is apologetic. We have been together 8 years and this never happened before. I think I need to leave but I don't know where to start. I haven't told anyone what happened.
<bot>: I was punched by my partner while I was sleeping. I think this is sick and twisted but I don't know how to leave.