In my experience the subconscious picks up subtle input during the conscious state. If you analyze your dreams you may be able to see what things it catches and re-interprets in dreams. It's often not the big thing you've been stressing over, but some little event that occurred which you dream about. If you unintentionally (subtly) think "oh, I am tired...I may not be able to LD" you might set that thought in the subconscious. So you want to subtly think "I will LD tonight." But I don't subscribe to going over and over that thought as it then becomes conscious desire not subconscious intent.