There's a longstanding dictum that says something along the lines of "Don't believe you're own trash talk." The leaders in North Korea are well aware of it. They don't follow or believe in Juche for a second, that is for the proles. They are interested in preserving their lives and their positions at the top of the totem pole.
Equipment wise, they (the Norks) don't even measure up to Iraq in 1991 as far as capability goes, and they have to be aware of that. They have a lot of soldiers, they may be heavily indoctrinated, but they don't have much money for training that many troops. South Korea, by itself, has modern equipment, thorough training, and something other than dear leader's memory to fight for. South Korea can count on a lot of allies, Japan, these United States, and others. The Norks seem to have even convinced their one ally, China, that they are a rabid dog.
The Nork leadership isn't that stupid.