You make changes as you can. You don't have to "succeed" the first, second, or fifth time, but any time you are able to stop for a time is a success. (check out the Prochaska model of Change---'Trans-theoretical Model of Change'---where no one is a failure...if you feel like a failure that just adds to the struggle. It is normal to want, but not want...you are contemplating change. Suggestion: read up on addiction, on your particular addiction, both professional and first person/or caring other experiences. There are numbers to call...I am sure you can find them on line.
Nicotine was my addiction---it took 5 or 6 attempts over a number of years, but now is a thing so long gone, I don't even think of it any more (and I was bad enough to dig through garbage for butts....). Is there something else you could spend the money on first? thus depriving yourself, for now. Keep trying. Keep reaching out. If you are up for it, some intense activities (running for instance, or skydiving etc) can become addicting & are generally healthy....