A while ago I was trying some memory experiments along these lines. I had a hypothesis that it might be easier to remember past dreams while dreaming, but to my surprise that didn't work well at all. Memories of waking life were more reliable, but sometimes amusingly out-of-date like Sivason described earlier. I also noticed a remarkable degree of reluctance on the part of my dreaming mind to perform this task, like it didn't want to have to remember.

However, the real stumbling block came whenever I tried to think about my sleeping body... and woke up. This happens every time. The minute I let my thoughts stray to the fact that my physical body is actually lying in bed, the dream dissolves and there I am lying in bed, even if I had no desire or intention to wake up. At this point when I'm dreaming I'm careful not to think about my sleeping body, because I've never found a way to do it without ending the dream.

Any suggestions?