If left entirely up to your legs, back, feet, and side, there would never be a jog that lasted long enough to do you any good. Your brain can envision leaner muscles, better conditioning, greater endurance, and that deep, rich feeling of accomplishment, but your individual body parts don't care one bit about that. They just want out. They want this over. They want a long squirt of water and a place to sit down.

There are certain sins and temptations that take all the strength you can muster. You push them out of your mind one minute, only to see they're back the next. They're like a fly in the house-buzzing and darting, landing out of sight, then zooming by again just when you'd forgotten about it.

It could be on the shopping cart handle at the grocery store. It could be on the collection plate at church. It could be on the iced tea spoon at your favorite Mexican restaurant. It could be anywhere-on the spine of a library book, on the canister at the bank drive-up, on the cup holder at the movie theater.

If you struggle with an addiction-be it substance abuse, or pornography, or gambling, or whatever-you certainly know by now that making a turnaround is not something that happens overnight. It takes a true change of heart and usually a good long time. Nothing easy about it.

The battle against sexual lust is sort of in a class by itself for most men. Other allures and temptations may buzz around us, but few if any can stir up this kind of struggle, shame, and enslavement. It can make us want things that seem irresistible.

In Game Plan for Life, Coach Gibbs recounts the story from the Redskins' 2007 season when, in an effort to ice the opposing kicker in the closing minute of a two-point game, he mistakenly called two timeouts in a row.

We all have a weakness. Probably a whole handful of them. It may be for something as relatively innocent as power tools or potato chips. Perhaps it's much more serious and destructive, like online pornography or a real problem with rage. But here's one thing we know about our weaknesses: if we were able to overcome them, we'd have done it by now. We either like them enough that we don't care, or we've tried everything and nothing has worked.

This article is excerpted from a chapter in Ravi's book, Deliver Us From Evil.

Truth is stranger than fiction, it is said, but as Chesterton has appropriately declared, that may well be because we have made fiction to suit ourselves. There is possibly a more disturbing reason for our estrangement from truth, particularly if that truth signifies a reality that is terrifying and unchangeable.