Oddly enough, with practice you develop a duel mode of experiencing your dream body/enviroment AND an awareness of your waking memory.

It is odd in that while waking this is something natural but in lucid dreaming it may take a few tries. In waking life we can daydream about the past while driving with little fear of not seeing the next cars break lights. It is a similar process in the dream and just requires experimentation. You divide your attention in the same way, keeping a portion of your awareness on the dream itself.