Have you ever smoked? Did you smoke for a number of years, then quit? If not, run this past one of your friends who did. Imagine cutting down... but never completely quitting. You're not allowed to cold turkey. You have to smoke five cigarettes a day: morning, noon, and night, with two unscheduled "snack" smokes. Never less- five smokes. But never more, either; if you cheat, have too many, you can't make up for it by skipping one the next day- it's not that easy. No, for every one you cheat with, you have to spend a week smoking the same five smokes, but half length cigarettes- just a couple puffs, not enough for satisfaction, then put it out. No matter how much you want one more toke, put it out, try to hold out 'til the next smoke... which will also be too short, until you've worked off that extra one you had.
If you're not a former smoker, ask one- there are tens of millions of us; statistically, I know you know one. Could you do it? Spend the rest of your life smoking five cigarettes a day, never more, never less?
That's what it's like losing weight.