I think rynkrt3, it's basically telling yourself over and over you are the best at lucid dreaming and you can and do have them whenever you want. You don't say it over and over until it is drummed into your head, you just have to at least pretend you believe it. Like deltz said, act all cocky and confident, that "Yeah, lucid dreaming is easy, I'm not worried or concerned about whether or not I will have one tonight, because I will have one. I have been practicing and trying and so now there is no way I won't have one tonight".

Just pretend you know you will have one. Think of it like your subconscious is listening to you, and is trying to do it's best to do what you want (it is actually). If it hears that you are a master lucid dreamer and you're going to have one tonight, it will try to have one, rather than just happen across one when you lay in bed at 4 in the morning not moving.