"Covet" is a weird word in modern English. It's one of those that preachers and Sunday school teachers are always called upon to explain. "What does the Bible mean when it says, 'Thou shalt not covet?'"
The usual and, I think, correct answer is that it does not merely mean wanting something someone else has. Looking at my friend's new car and thinking, "Man, I wish I had one of those," isn't coveting. Rather, it's wishing that you had the new car instead of your friend. Or feeling ill toward your friend because he or she has the new car.
I'll give you an example. Today, it was hot and humid. Today, my grass was really long. And so, today, I mowed my grass in the heat and humidity. We have a large yard and I have a push mower (self-propelled, but still). It was sweaty, nasty, miserable work. Well, about halfway through cutting the back yard I happen to glance toward the street and spy, through a gap in our fence, a pickup truck towing a boat. It was a nice boat. Sleek, shiny, big, and by the look of it, fast. And in the space of a couple of heartbeats several things ran through my head. First, I thought of how nice it would be to be out on a lake somewhere swimming, tubing, maybe doing a little fishing (not that I fish, but we'll roll with it), or just tooling around in that shiny boat. Second, I thought of how unpleasant it was to be pushing a mower back and forth across my ridiculously long (and still slightly damp from recent rain) grass in the heat of a mid-summer sun at high noon. Then, putting the two thoughts together I glared and the tail-end of that boat as it went out of sight and grumbled, "Jackass."
And that ladies and gents, is what "covet" means. I didn't just wish I had a boat. I didn't just see the boat drive past my house and think how much I'd love to be out on a lake instead of cutting my grass. I saw that boat and, for a fleeting moment, actually felt ill toward the people in the truck because they were getting to go out in their fancy little boat while I was stuck cutting my stupid grass in the baking sun.
So there it is. That's my spiritual insight for the month. It may not be especially profound, but it sure whapped me upside the head under a hot June sun.