Going from a normal carb diet to a very low carb diet can produce intense changes in your mood, feeling of well-being, ability to focus and even your experience of reality. As everyone's body is different, we can't say that "Anyone on a low carb diet will experience X effect" but we CAN say that most people on a low carb diet will experience SOME effect. For me, personally, going into ketosis is a death sentence. I have a "man period" where everything pisses me the fuck off, more so than any effects I've experienced from juice.
Going on CKD, People report elation, irritability, increased focus, mental fogginess, etc. Basically, just about every end of the spectrum. Intermittent fasting can have a major impact on your productivity and ability to focus as well. You (or at least, I) get used to the change after about 7 days as your body fully adjusts. And for what it's worth, I absolutely cannot sleep unassisted on CKD or PSMF... Which probably contributes more to the anger and irritability than the lack of carbs themselves.