So today is my quit day, only couple of cancer sticks left and I'm done. Hopefully. Keep your fingers crossed.
Best of luck.
A little late to the party, but my advice whenever this question pops up is always the same, and while it's definitely not applicable to a large swathe of people, it was a simple fix that worked wonders for me.
Take a four-day weekend. Block everyone and everything out of your schedule for the four-day weekend. Find an all-consuming game. Play that game all of the four-day weekend.
It sounds reductive (and dumb, when you put it in terms of a videogame), but the most powerful tool for quitting smoking is an urge that's stronger than smoking. You need something that can literally (semi-literally) keep you glued to the screen, where the next match, or the next turn, or the next level is enticing (addictive) enough for you to not go out for a cig because all you want to do is to keep going with the game.
I can't remember for sure, but I think I did it with the first Pillars of Eternity -- CRPG revival was my cure. I dunno what your gaming vice is, but if there's something out there that you know could easily take over your life for 50+ hours, get on it. Breath of the Wild, God of War, first time battle royaling with PUBG, Warframe, whatever. Souls games always suck my life away when they come out, maybe if you haven't hit Sekiro yet that'd be a good option. If you have to buy a new console to play something you've been holding out on, I say you go for it, because it's still cheaper than smoking and that new console and game might be all it takes.
You just need something to buy you 50 hours of distraction. 50 hours is 3+ days, and the fourth day is when it starts getting easier, when it's more habit than addiction. After the fourth day, it really is mostly habit, and from then on out it's easier by the day. Remember, you're only like, a month away from being drunk at a party, going to bum a cigarette, and being disgusted at how gross it is. A month is nothing.