I read a book on self-hypnosis a couple years ago. It said the subconscience may be uncooperative if you sound demanding towards it. Don't say "make me have a lucid dream", instead, say "You want to give me a lucid dream" or something like that. Youre supposed to sound optimistic and suggestive. (I read that book a while ago, so i dont really know if i remember that perfectly haha.. but it was something like that)