It is not OK to covet your neighbor's wife and it is not OK to lust after your neighbor's wife...or your own wife, because, according to my confessor, "lust" isn't merely sexual attraction but a greed-based drive to possess and to please one's self at the expense of another. Sexual attraction ain't a sin; it is a beautiful and necessary part of "natural law." 

Lust, on the other hand, is unnaturally ordered  in that it regards self over the other, whether she be your wife, your girlfriend, or that woman in Tokyo. It is focused on the primacy--often even the sole end--of possessing another for pleasure. There is no mutuality in lust.  There is no respect, tenderness, or caring. 

Lust degrades, demeans, controls, and imposes. It is to intimacy what pornography is to art. 

Strong sexual attraction, spiced with fantasy and longing, can sometimes lead to lust, but it is usually not synonymous with lust. 

"I'm lost in a sweet dream..." as you and John Sebastian sing in your bands.