There's a nice Chazal about the fact that appreciation of a spouse is contingent upon faithfulness in the heart:
"kol hanosein eynov b'mah she'eyno shelo - ma she yeish lo, notlin mimenu - whoever puts his eyes on that which is not his, even what is his they take away from him" - in other words, there is a bracha we get to appreciate and enjoy the attractiveness of our spouses. It is from Hashem. We can't even lust our way to it, for that lust will eventually spill over onto other people.
Should I choose to be masbiyah eynee with a lust image (of a real person or of a picture), it is always at the expense of my happiness with whatever I've actually got. Whenever a lust opportunity comes up, I have a choice in that moment: do something in this moment that will increase my appreciation of my wife in some respect (take the actions of love) - or take this lust and use it - and as a result want it and believe in it even more than I already do. Which will it be? Often the addict chooses poorly...till the pain gets too great. Then he is really, finally, in trouble. But it is the best possible trouble to be in, and that pain opens the door to recovery.
[The actions of love can be calling my wife just to say "hi!" and ask how things are going/daven for her real needs/get back to the shopping I was doing for her in the first place before the 'image' came along, whatever. Being useful to her. She's my wife! Don't I want things to be better for us? Well, this is the only way....]