Isn't this how we are with God too. The things that He has set off limits to us, just starts with a "lick" so to speak. We have that thought about whatever and pretty soon, we are dwelling on it. Then we think that we can have just a "taste". Then the taste isn't enough either and we fool ourselves into thinking that just ONE is okay. When the Lord brings conviction, we justify our behavior to ourselves, making it easier to do it again, or have another.
Satan usually brings just enough truth into the situation to make it easier for us to slip, to fall. That is why we must be so on guard. He comes to kill, steal, and destroy. But even with the things the Lord has set off limits to us, they are meant for our protection, and for our good.