"You shall not covet your neighbor's house; you shall not covet your neighbor's wife, or his male servant, or his female servant, or his ox, or his donkey, or anything that is your neighbor's."
The final commandment delves deep into the heart of man. Instead of being focused on outward actions, such as theft or murder, it moves toward the inner being.
Coveting is a matter of your thoughts and your inclinations. Not only is it wrong to steal, but it is wrong to desire what does not belong to you, that is, it is wrong to have theft in your heart and mind. One reason why this is so, is that coveting what you do not have is like disagreeing with God that he has provided enough for you.
The proper attitude might look something like this: When a man says to himself, "It would be nice to have such and such, I will work hard so that I can afford it, and if God wills I will attain that thing." This man is not disappointed if he does not attain this desired thing. His desires do not rule him.