The Bible says God is light. "Light" is a metaphor for Truth. Truth meaning the real way the world works, and the real way it should work. We know that God made the world, and he made it agree with the Truth. The world, at creation, actually functioned the way it was supposed to. But the world doesn't function the way it is supposed to now. And we don't function the way we are supposed to.
When we choose to follow Jesus, when we change, making Jesus our primary allegiance, Jesus fills our hearts with his presence, giving us power to live as we were designed to live.
The reality is: we do not live as we were designed to live, even after we switch allegiance. Whatever got broke in the hearts of people, when sin was released into the world, is still broke.
When Jesus dies on the cross, and we he rose, his Spirit and his Body were released into the world. He released his DNA ... and his DNA creates his proteins and enzymes to re-manufacture the world.
We do not live as we were designed to, because the re-manufacturing process is in progress. Moreover, there are forces that want to hinder this process for their own purposes. This hindering is the essence of spiritual warfare. Although it can be, spiritual warfare is not generally some ugly, demonic manifestation. It can be as simple as introducing a non-Jesus-like thought, getting it considered, entertained, invited out for dinner and, maybe, asked to move in. And I am willing to bet that we will all at least once have dinner with something non-Jesus.
Of course, it would be best to "stay on our diet" and refuse the invitation. But what happens when we come out of our trance in the middle of dessert? I am beginning to wonder: if short-circuiting the temptation cycle early is the most important step, then is the second most important step our response after we fall?