Since it was asked earlier,what is the importance of lucid dreaming,I thought I post this.I have been re-reading Tibetan book of living and dying and I came across this in chapter 7 about explaining the bardos.

"Of course the bardos of death are much deeper states of consciousness than sleep and dream states,and far more powerful moments,but their relative levels of subtlety correspond and show the kind of links and parallels that exist between all different levels of conciousness.Masters often use this particular comparison to show just how difficult it is to maintain awareness during the bardo states.How many of us are aware of the change in consciousness when we fall asleep?Or of the moment of sleep before the dreams begin?How many of us are aware even when we dream that we are dreaming?Imagine then,how difficult it will be to remain aware during the turmoil of the bardos of death.
How your is in the sleep and dream state indicates how your mind will be in the corresponding bardo states;for example,the way in ,which you react to dreams,nightmares,and difficulties now shows how you might react after you die.
This is why the yoga of sleep and dream plays such an importanat part in the preparation for death.What a real practitioner seeks to do is to keep,unfailing and unbroken,his or her awareness of the nature of the mind throughout day and night,and so use directly the different phases of sleep and dream to recognize and become familiar with what happen in the bardos during and after death.
So we find two other bardos often included within the bardo of this life:the bardo of sleep and dream,and the bardo of meditation.Meditation is the practice of the daytime and sleep and dream yoga practices of the night."

Hope not too many typos,don't feel like checking..