Dream Analysis

As Mr. Stewart was talking about, last night I tried to actually process and remember my dream, I was successful. Although I'm not going to express my dream, it makes me want to learn more about the dream process. As it's said that there is 2 stages to dreaming, the stage were barely anything happens and the REM stage. This makes a big question come up in my mind about dreaming. Usually in my dreams, if it's a nightmare, the bad things happen at the end and you wake up right before something bad happens to you. Considering the REM stage is after the slow EEG stage, is that why we wake up? Or what causes us to wake up right before the bad things happen? Although the world may never know, I would really like to find out. I believe that the REM stage causes us to wake up before we reach the climax of our dream. What do you guys think?