I'll give you my honest opinion. Clearly, the yetzer hora went after you in a big way. He didn't want you succeeding. And even so, you fought back, and weren't mz"l.
First of all - have you destroyed what you worked for in the last 89 days? Well, the chofetz chaim says about lashon hora that if someone restrains himself from speaking, even for a minute, he gets access to a spiritual light that even the angels cannot fathom. That's even if he can't control himself, and after that moment, says the lashon hora!
It would seem to me that in our battles, the same would apply - I don't see why not. So even an instant of restraint, of waiting, of beating the yetzer hora, is a huge victory, worthy of celebration. 89 days? No one and nothing can take that away from you.
You fought a long battle, and that's tiring - and now, after having spent so much time and effort, you probably feel drained. But maybe that's your test. Up in heaven, your test wasn't the last 90 days. Maybe Hashem said that you're stronger than that - Everyone knows that Reb Yid can do 90 days. But what if he's pushed down, and he falls - that's the test. Will he have enough strength to get up again?
And clearly, Hashem knows that you do have the strength. And although I haven't been here long, I'm impressed by you, as well - fighting a difficult battle, already having a feeling of "giving in," you still held yourself back from going to the next level of mz"l, which to my mind is HUGE in so many ways!
As for hope long term, I don't know enough about addiction to talk about that (but hey, here I am doing so anyway!) - but it seems to me that at the rate you're going, you're looking at p* (I'm sorry, I love using random symbols in place of letters) about 4 times a year. Now yes, that's a tragedy, and it also makes it very easy to slide down a very slippery slope. But it's also a huge victory - You're averaging four periods during a year, when most of us on here have been used to constantly being involved in these things.