It’s downright annoying, when something is bothering you, to have one of your friends say,
Well, try not to think about it. Right. Have you ever tried not to think about something? It’s pretty well impossible, because all the time you are trying to not think about it you are thinking about not thinking about it. So you’re still thinking about it, right? It’s like actively trying to forget something—the effort of not remembering something automatically remembers it.
Nature abhors a vacuum. So when you empty your mind of bad things, they have a habit of coming right back. So, how do you not think about something. Well, the answer is deceptively simple. You do it by thinking about something else. That’s all. It’s pretty hard, in fact, to maintain two strains of thought at the same time.
In the same way, you would think that once Jesus had healed someone of a terrible disease, or cast a demon out of them, that their problems were solved—permanently. (After all, when Jesus fixes something he fixes it right.) But if you think that, you would be wrong. Emptying your life of the evil that has been there leaves a hole. And unless that void is filled with something else, you’re very likely to go back to what is familiar and comfortable. Jesus, having cast out some unclean spirits on an occasion gave this warning, found in Matthew 12.