I am a huge believer in forgiveness, to a point that if someone can forgive, but not able to reconcile, that person is not a person anymore. Subhuman, if you like.
To err is human, to forgive is NOT devine, but true humanity. Anything less than that is something Im not wasting my time entertaining such a subhuman thought process.
I don't know if you're still around, Flashman, but if so... there's your problem, that bit in the quote box above. It's wrong. And not just wrong, but utterly wrong, wrong enough to explain why R is failing for you.
No one is owed forgiveness. The idea that you are automatically owed forgiveness for your transgressions minimizes your transgressions. People aren't "less human" or "subhuman" if they choose not to forgive. Forgiveness is a gift... and everyone has a free choice as to whether they'll extend it and to whom.
The fact that you seem to believe that forgiveness is owed to you as a condition of humanity indicates that you are suffering from a grandiose state of ENTITLEMENT. No wonder it's so easy for you to backslide. There's no method by which you can gauge the seriousness of your transgressions when you believe you'll automatically be forgiven for them.
I'm not saying these things to be hard on you. I'm saying them on the off chance that you might actually LOOK at what you're saying. It's not until you understand where you're going wrong that you can make it right. Your BW has no reason to forgive you when you can't even begin to understand the significance of your wrongdoing. It's too easy for you to backslide into porn because, for you, you don't believe there's a consequence which doesn't dehumanize her. You think she owes you forgiveness, so what the heck is there to stop you from downloading the nasty? There's no cost to you except that she'll be mad for awhile. But you've survived that before, so no big deal. Do you see how this misinformation you've been telling yourself about forgiveness influences your bad choices?
Forgiveness is a gift. When you start treating it that way, as something precious, a form of grace that you really didn't deserve, maybe you'll start seeing some change in yourself. It's not hard to NOT look at porn. It's the absence of an effort. Nothing required. But it's pretty easy to give yourself permission to do something which HARMS your wife and your marriage if you believe there's no consequence and that it shouldn't be held against you.
Bear in mind that even in Christian forgiveness, the sinner is required to redeem himself, to refrain from further sin and to be heartily sorry for his transgressions. And just as you can't set the terms for forgiveness to God, you can't set them to other people. We each decide what we'll forgive and what we won't. Your BW gets to decide what she'll forgive and what she won't, and your proclamations upon her humanity won't change the fact that it's HER natural born right to do so.
For your part, making this adjustment in your mind can help you to make better choices if the future and teach you to show better appreciation on occasions when you do encounter grace.