John Piper recently made a good point about understanding Satan's strategies:
He's got one lie, that he says in 2 ways. (1) God is bad. (2) Sin is better.
No matter what test or temptation we face, we will hear one of those lies in some form.
"God is not faithful or wise" or "That computer or food will satisfy you more than..."
In a word, the lies goes like this: "Sin will satisfy you more than God".
Both God and Satan make promises, but in every part of life, we choose whom we think will be more satisfying and whether we believe one or the other. When you look at it that way, many of the gray areas become less so.