Well, my understanding is that it's not far off from letting your thoughts control you as opposed to training yourself to be more aware of them. Throughout the day you might pay little attention to what you are doing, but when you practice mindfulness you see that your initial disposition wasn't too dissimilar from "unconsciousness." 24hr. lucidity doesn't mean you're dreaming the entire night, it also involves awareness during dreamless sleep. This is what sleep yoga aims for and is associated with a profound experience of bliss and emptiness. It's possible to shift from dreamless sleep to dreaming (and vice versa) without losing awareness. It's not tiring at all, it's liberating (I think, haha ).