I've been working on this topic for a while – at times abandoning it because it can be a depressing and emotionally-fraught thing to think about. But, with everyone out there making New Year's resolutions, this seems like a good time to post on it.
The way temptation works is pretty similar, no matter what the object – food, drink, smoke, video games, shopping – whatever the particular individual's weaknesses are. The want pops up in the mind – and the closer and more available the object is, the more often it will pop up in the mind. And you say “No”. Good for you. Then, it pops up again. “No.” And again, “No” Then, there comes a point that unless the object is completely out of reach, you're gonna cave. Brian Wansink, author of Mindless Eating says that the average person makes 200 decisions a day about food, including each of those times we say “No.” His whole system is built around making it easier for the idea to not pop up, and for you to say “No.” when it does. The point is that so-called “will power” isn't just a matter of dropping a bad habit once, or limiting it to a reasonable level once, it means you have to do it over and over, maybe for a lifetime. It's a really boring and bleak way to have to live.
So, eventually, we will cave in to our desires. It takes something big and powerful for the desire to go away. I was a smoker for years, since I was a teenager. I continued to smoke as it fell out of fashion and smokers were shuffled into unpleasant corners, then to the cold outdoors. I continued to smoke while doctors gave me lectures every time I or either one of the kids had to go in for an upper respiratory infection. I tried to quit several times, but the reward of being a non-smoker just wasn't worth the misery of the nicotine fit. What finally got me to quit was that the smoker's cough became so severe that it interfered with my ability to teach – and that, I couldn't stand. I switched to nicotine gum, and later, lozenges and stayed on those for years and only finally quit them when I couldn't afford nicotine any longer.
In some ways, addictions are easier to kick than other bad habits, because the physical craving does go away eventually. (Although I still miss nicotine from time to time.) Food is probably the most difficult, because it's not a matter of getting something “bad” out of your life, but a complex set of choices that often has consequences for your social life and even your closest relationships. When you stop eating (or drinking) with someone, it creates a distance -- which can be a good thing or a bad thing, depending. The alternative of sitting there with something permitted while everyone else indulges is uncomfortable, and probably not sustainable for long.
Other desires fall in between those two, but they still involve the same process of saying “No” to yourself repeatedly. You give yourself rules, limiting the tempting object to a certain time of day, or to a number of times a week. Or the ultimate in obsessive rule-making – the calorie count diet, which requires you to keep track of virtually every mouthful you eat. It does work to a certain extent, though; it's easier to postpone or limit a desired object than it is to deprive yourself forever. “I'll only drink after 7:00”; “I'll only spend $50.” “I can eat this and still be under my calorie limit.”
I don't think anybody has ever been successful at making changes when feeling bad about themselves. That's the reason shaming and nagging are so ineffective. It's better to start from a place of self-nurturing and to proceed with a commitment to mindfulness, rather than the tension of white knuckles and forcing yourself to “be good”. Will power works only in the short run; it's brittle and can be easily shattered. I don't know if metta and mindfulness are more effective as tools in reaching a specific goal, but I do know they are effective at creating more happiness in your life – which is pretty much the end of all those goals.