Hmmm, that's a good question. Hopefully it's not a true story, so FICTION... but as for a genre... I have a list of 10 genres I found somewhere (adventure; fantasy; SF; historical; literary; humor; horror; romance; thrillers; westerns), and of course they all have sub-genres... but the only one I could see your story fitting in would be LITERARY, as that covers drama.
Your story isn't blatantly dramatic (or do I mean overtly? Same difference I guess), but drama is about conflict, and there is conflict between your protagonist and his habit ... though it seems like he is almost at the end of the struggle, that he's barely resisting now (and did he ever really, or was he just kidding himself, breaking promise after promise). He's now letting the habit have more and more control, not really fighting it any more, so much as trying to keep ahead of it ... that's my takeaway anyhow 😁 , is it what you were going for?