I quit and restarted numerous times before quitting for good about 20 years ago. I found that (presumably because your body runs in cycles) it's easier some times to quit than others. Some days, you just crave the stuff less. That's a good time to quit. Maybe it's stress or some biorythym or some combination of factors, but might as well make it easy on yourself and quit while the quittin's good. Chewing--now that's a jones. A bad one.

As for booze, I'm a heavy drinker, but I quit cold turkey every Lent, and it's easy. Six weeks of abstinence and I'm always happy to return to my old, bad habits, but apparently not because I'm strung out.