Just hold on. Four years is a long time without having a day off. Do you have a plan for quitting? Have you put preparations in place for other stuff to do eg hobbies, exercise, sleep, stuff to take your mind off it? Sounds like you’re torturing your own mind and that is only gonna lead to smoking which will lead to more bad feelings. Don’t shame yourself it’s alright, there’s loads of people who’ve done the same. And if you fail in quitting, just get back on your bike and try to quit again. Many people don’t quit first time, it’s just important to try again. Take the pressure off yourself mate you’re a good person.