I started smoking cigarettes when I was 15. By the time I was 17, I couldn't taste them any more, and I wished I could stop. I then started trying to quit. Sometimes, I would quit 20 times a day. I deplored my weakness deeply and often. A lot of self-hatred was engendered, but didn't make much difference.
By the time I was 30 I was married, and my wife started some asthmatic bronchitis problem that had her sitting up coughing in bed all night, every night, from December to May. I thought maybe my smoking was irritating her lungs, so (for her this time) I quit. It was not easy; the pain of separation did not dissipate in a period of weeks. Every five minutes of every day for three months I thought, "Well, that's done; where's a smoke?" Or, "I should think about that; now's the time for a smoke." Or, "A smoke would go along well with this relaxing moment; where... oh, crap." After ten months I was way better, only thinking of smoking maybe four times an hour. After a year and a half, I was better than that, but not over it, and I started cigars. My wife's bronchitis didn't seem to lessen for my not smoking.
Five years later, my second daughter was diagnosed with a mild asthma, and I figured I should quit the cigars. For her. So, I relived the earlier experience, and three or four years after quitting, I only thought about smoking a couple of times a week. Did I mention that during the five years of cigars, I thought about quitting hundreds of times? Naturally.
The moral of the story is that if you can't quit, keep trying. It may be some dumb extra motivation that gives you the extra push that makes it successful. Maybe sheer luck will bless you, and you will find your weak motivations become inexplicably sufficient to the task. Maybe an aid, like patches or gum or hypnotism will get you over the hill. Whatever it takes. It's a seriously addictive product.
I quit the cigars 20 years ago, and I don't think of them any more. However, if I were diagnosed with a terminal illness, I'd be back with the cigars. Unlike the cigarettes, I never stopped liking them.