If your friends know you as any kind of habitual smoker, they will probably find the prospect of you cutting down nothing short of laughable. In which case, you find yourself in a uniquely profitable position where you may be able to make a serious amount of cash at the expense of those who have little to no faith in you. If they don’t believe you can do it, suggest placing a wager on it. If you lose, you owe your stoner circle a massive bag of premium bud. If you win, you smoke for free for X amount of time after doing your stint.