A couple years ago, I quit nicotine. Here are some things that helped:
Going cold turkey. I found this better than gradually tapering off. I tried gradual, but found that it gave me too many opportunities to change my mind (given that I still had nicotine in the house.)
Treating myself in other ways. I watched a ton of TV, drank a ton of coffee, ate a ton of fast food. It helped reassure my brain that there are other sources of dopamine in the world!
Accepting that I was going to be miserable for a while, and that was okay. I had read enough blogs and watched enough videos to know this is a normal part of the process, and there are better things on the other side.
Getting extra sleep. This was much needed, because I found I was a lot more tired at the end of the day. Some mental processes that had been pretty automatic required more consious effort (this feeling went way over time), and that was pretty taxing.
Running. Those sweet endorphins or whatever chemicals you get from working out… were appreciated. Also, I always sleep better on days that I run, so this was helpful in boosting my energy.
Imagining myself as a kind of Orwellian prisoner, whose is being forcibly brainwashed into forgetting about nicotine. (This is what nicotine withdrawal feels like.) Forgetting really is the goal. For a while, I would compulsively google blogs/articles about quitting, probably because I wanted to keep the idea of nicotine in my mind (didn’t want to let it go.) But the more you think about it, the more likely you are to start using nicotine again (in my experience.)
…actually, even addressing this topic at all might be triggering. Forget I said anything!