"Battleworn" recently posted to someone on our forum who was struggling with falling and trying to get back up again. What he writes below is perhaps the most important Yesod in beating this addiction in the long term.
One of the great tzadikim rendered the pasuk "Velo sosuru acharei levavchem ve'acharei eineichem" as follows. Don't untie your kesher with Hashem after (acharei) you went after your eyes and after your heart. The greatest nachas ruach for Hashem is when we keep fighting even after we've been beaten.
What really counts, is not how long you can stay clean, rather how consistently you keep trying your hardest!!
And here's another powerful post from Battleworn about his own struggle (edited a bit for clarity).
I was really starting to feel "up" lately. When jack hit 90 days it gave me an additional boost, then came the R' Tzvi Meirs daughters chasuna and I really started feeling like I'm getting back to the good days of Davening, learning, shmiras einayim and simcha. The menuval was of course not ready to give in without a serious fight though. So first he got me down with his usual weapon of some trouble at home. Then he filled up my regular email box with a bunch of spam, which were all links to bad sites. I didn't click any of them but having it put in front of me like that was very unsettling. Then he got me super curious about the kind of stuff that I wrote about in my story (like "what happens if you search in images with this or that word with safe search on?"). Baruch Hashem I wasn't MZ'L - not even close, I didn't go to any porn sites and I didn't gaze at bad stuff. But I did see a lot of bad stuff in passing, and of course I was left even more unsettled and desperatly curious than before. There was this one thing that I just desperatly wanted to check out the next time I was by the computer, and I didn't feel like I could control it.
Then I went to the last Sheva Berochos (of R' Tzvi Meir's daughter). As I danced my kishkus out, I realized that I'm totally ready to die for Hashem, but to shecht the y'h is harder than dying. But after dancing enough, I made two very strong kabolos. I will not play around with searches and stuff like that at all for the next two months (I will only search for something that I specifically need), and I will not ever pursue this stupidity that I was so curious about, even if I have to suffer or die from it. I came out of that Sheva Berochos a new person, and right now I'm realizing that once I made these kabalos, this stupid curiosity that wouldn't leave me alone for a minute for two days, suddenly went away.
We can all learn from what Battleworn writes above, what makes a soldier truly battleworthy!!