I only have 5 days, so my advice might be abit offtrack so anyone correct me if Iam wrong for my own feedback aswell.
Now there's a difference between what I learnt and what I implemented.
I've learnt that you can't just make a choice and expect sobriety. You literally have to do work work work.
And the problem is that everyday is unexpected, and then comes a month (longest I've been) and you suddenly get this dread that "I've worked this hard all month, and there's another month ahead?"
I suppose Ive learnt that my failure to quit attributed to all my failures. I've always started something, And then got sick of it and stopped it before achieving my goals. The goal always fades away for me over time, that's what I have to work on.
To answer your question, the external change is simple( say no, Change routine, do a hobby) the hard part is the psychology behind it.
Ironically, I started alcoholism, but I can't quit(judging from previous attempts)