The common belief throughout many psychoanalysists is that deja-vu occurs when the individuals current surroundings remind them of a dream in which they wish to repress and forget due to uncomfortable empathy or ill-memories that is associated with the dream.

It is also believed that it is induced by interruption of repression, when trying to forget a moment or thought and move on, and then immediately be hit with it again. It happens all the time to people, typically with short-term memory; at work, doing small tastks, looking for a movie to rent, shoppping, etc. So, when you move onto the next task, and you are suddenly, subconsciously, reminded of the previous task that you have forgotten due to the fact that it was only stored in short-term memory, it can cause a deja-vu feeling.

Then, of course, people believe it is the feeling of being reminded of another plane of existance or the future.. etc.

Although, I agree; lucid dreaming will help with control of deja-vu in both controlling it and extending it, or completely abolishing the feeling of deja-vu all together. Wouldn't it be nice to be able to tap into your memories and thoughts without any interruptions or external influences to disrupt your train of thoughts? It would be the perfect mind..

Hope I've been enlightening.