I just read about this in the newspaper the other day.
Kind of feels weird, because for the longest time I was not aware that lucid dreaming was a rare phenomenon (Or rather I did, but not how rare it was). I get lucid dreams on a pretty regular basis and if anything I'm more freaked out by the non-lucid ones since it's one of the rare moments I have a disconnect with myself.
It's certainly not an endless degree of lucidity, though. I sort of have to outpace my unconscious mind, which can be a hit-or-miss ordeal.
By the way, so far I've been diagnosed with depression and some kind of slow encoding learning disability, if that gives any possible insight.
Oh and, I know absolutely nothing about Yume Nikki, so don't assume I'm a board constant.