Gut Moed TshuvaYid !
Sounds like you're now in the thick of the battle, so I'll share what works for me for short-term survival. Hope it helps.
There's an old saying, "War is 90% boredom and 10% terror". When you're in the thick of the battle it feels like you can't hang on much longer, and that's true. But most battles have lulls with time for rest and regrouping. I'm sure you sometimes went to sleep feeling very stressed and woke up the next morning a changed person. "One day at a time" is not a cop-out, it's a reality to our changing emotions. Sometimes I read (or watch on DVD) war stories from WWII, and when I see what the people (including the soldiers) went through then I look at my challenges in a whole different way.
Another strategy is redirecting the emotions. The Gemorah says, "if your Yetzer Hora meets you, "pull him into the Beis Medresh". Not to leave him out in the street but "pull him in" and use those emotions in a positive way.
I don't know whether the following strategy is legitimate but it's worked for me in the past and it may help you. When I've reached the point of giving up, a controlled retreat is better than a complete surrender. In any war certain battles are more strategically important than others. I've always felt that long-term success of Shmiras Habris depends on success on certain days more than others. For example, Shabbos, Yom Tov, Chol Hamoed, and Rosh Chodesh because of the magnified effect our actions have during these days, and also the 13 days of Sefiras Haomer which correspond to "Yesod" because they affect the Yesod of the upcoming year. So if I'm correct, it's better to win a battle during any of the days of Pesach and then fall one day after Pesach rather than vice versa. So if you know that you're about to fall during one of these days, and the only thing that can save you right now is the knowledge that you'll have a "vacation day" soon (because sometimes we can hold on longer if we know there's a time limit to our deprivation) then that strategy may work. But it may backfire for some, I may be an unusual case.