Stopping is 90% a matter of will power, you must stop making excuses to yourself and others and just tough it out. Like a root canal, do it and be done with it.
I've had 4 root canals and I've quit smoking. Quitting smoking is much harder. Root canals are completely painless, I fell asleep during 2 of them. If you have pain during the procedure, you're seeing the wrong dentist.