Principle 7: True fulfillment vs. false fulfillment
The Yetzer Hara's job and goal is to cause us damage, and to do this he was given permission to use pleasure and "Sipuk" (fulfillment) as a bluff to be able to harm us. Otherwise, how could he possibly do his job? We would tell him to get lost! But we must understand that his seductions are like a terrorist offering us a piece of cake to ensnare us. We know he doesn't mean the cake, he means to use the cake to damage us somehow. Only pleasure that is tied with truth has a Kiyum (lasts) because it can make a mitzvah complete; for example, eating meat on Yom Tov or the enjoyment we experience on Shabbos. But pleasure that is tied to Sheker has no kiyum, which explains why when the pleasure is over, we don't feel any fulfillment. And we also don't talk about it with those who love us, with those who want the best for us, because we know that it was just there to damage us. And that's also why we want it again not long afterwards, even though we just had it. After all, if it was truth, why isn't it there anymore? Because we feel a void, and so we look again to fill this void with another false Sipuk (fulfillment).