The proverbial Slippery Slope seems to be the lesson in this letter. The dangers in subtlety, and how we can land in the middle of a spiritual wreck without even knowing how we got there. And, clearly, the demons understand this better than anybody.
The dude in the story has, not completely unexpectedly, reached a level of 'adequacy' in his spiritual walk. Ok, sure, he has some stuff left to get with God about, and he feels kinda bad about that. But, he still goes to church (when he can). He still reads his Bible (OK, well, it's somewhere in the house). He wrote a check to a charity last month. It's all good (enough). And, like Screwtape says, as long as we maintain the "habits of a Christian", we will think we are one.
So, the demons' plan at this point is to just let the guy slowly slide away from God, totally on his own, just a little at a time. They're going to stay pretty much hands-off at this point - kinda like those videos from 'up North' (Southern terminology) you see on the Weather Channel when a car is sliding on the icy road and the driver takes his (her) hands off the wheel and just lets the car end up wherever it ends up. And it's usually not someplace good.
We all slide, and it's not like we don't know we're 'sliding'. In the car, we'll just ride it out. (I'm not going that fast. And I am wearing my seatbelt. I'll be OK.) Same thing spiritually: As Screwtape says, any "dim uneasiness" (aka 'sliding') we sense in our relationship with God we just deem "temporary and revocable". So, no need to over-react here. "This too shall pass" which, BTW, is not a scripture of the Bible.
And, with all this slippin' and slidin', here's what can happen next: Guilt. Not the kind that makes us fall on our face and ask the Father for forgiveness and mercy. But, the kind that compels us to trade substance for superficial (so we don't have to really deal). The kind of guilt that drives us to sort our sins into 'tall, grande, or venti' in order to make ourselves feel better. Essentially, we end up doing a whole bunch of nothing. And nothing separates us farther from God, than Nothing. And that's true whether you're from Up North or Down South.
Lord, help me to pump my brakes and get a handle on any sliding I'm doing right now. Amen.