So try a week. 5 days. 3 days. Whatever you think is attainable. Even a day if you think that will be an achievement. If you're falling every day, then a day is the best way forward. Is a day not the biggest achievment there is?
Here's something that Dov wrote somewhere else on the forum.
Dov
'One day at a time' does not mean 'just stay clean for today, hold on one more day and pretend tomorrow's coming up for air will never arrive!' That is just plain lying and does no good in the long run. Rather, I think it means that today is really all you have. Hayom is repeated so many times in sh'ma and the Torah because today is always where you are. Yesterday's failure is not any of your business and tomorrows failures are not, either. They are G-d's affair. We live in the present....if we are mature enough and humble enough to do so. Usually we are not, though, and insist on 'fixing the damage' first. Our very common focus davka on 'Tikunnim' before stopping and living clean for a few years, is really nothing but childish gayvoh in religious garb. I know and have been there. Oh - and it does not work, too.