I "only" smoked for about 5-6 years, but I was a pack a day. I quit cold turkey. To me it really wasn't that hard. Just don't buy cigarettes, and if you can help it, don't be around people who smoke. It sucks for a month or 2-3, especially in those moments where you normally always smoke (morning coffee, after dinner, etc), but idk, as long as you can resist the temptation to buy, you're good. There's so much time usually in between thinking "I'm gonna buy cigarettes" and actually doing it where you can talk yourself out of it.
Also, get some lollipops or something. Toothpicks. Anything you can put in your mouth and suck on. Dicks. Just going through the motions, even without inhaling nicotine, really helped me.