I remember once reading and even watching a video about a meditator talking about a breakthrough that happens during meditation (I can't quite remember the name it is given though and why it happens), which can be extremely blissful for some, extremely scary and traumatic for others (visions of death and so on), and neither blissful nor traumatic for many.
Maybe the "Dark Night" that this person mentions, has something to do with that breakthrough coming upon the meditator as scary and traumatic?
On another note, to a certain extent all of us here, are currently walking in this "twilight", that's located between complete ignorance and the final knowledge and release of Nibbana. Many people around me, are far from the spiritual life, they indulge in the senses because they don't know (or don't want to know) any better. For them, "ignorance is bliss", and although they suffer terribly according to the Buddha's definition of suffering, for them they just live their lives to the fullest and make the most out of it without worrying about what tomorrow will be made of.
For us here who are sensitive to the Buddha's 4 Noble Truths, this state of being described above is hardly conceivable, as we understand the preciousness of human birth according to the Buddha's guidance, so we want to get on with the practices that will lead us to Nibbana, and these demand a discipline of body, speech and mind that wordlings do not care about one bit.
As far as my experience goes, as soon as one steps on the path, one is no longer fully ignorant, yet one is not yet fully awake, and this "twilight" situation can indeed make one seem "grouchy" when he/she gets to be around regular wordlings, if you see what I mean.
"This path is a thorough investigation and understanding of the limitations of the mortal condition of the body and mind. Now you're developing the ability to turn away from the conditioned and to release your identity from mortality." Ajan Sumedho, "Mindfulness, the path to the Deathless."