There are many layers to addiction. There are elements of habit. Everyone else has a pack of cigs in their sleeve, I want to be a cool kid, so Ill hang out with the cool kids and smoke when they smoke. Everyone else is taking a smoke break, so I'll join them. If it makes you sick and you decide it's not for you, you may be able to break free without experiencing chemical addiction. But after regular use the nicotine changes some brain chemicals around, and then when you are out of cigs, your skin crawls, and you snap at people until you find a butt in the ash tray, or make up an excuse to go to the store. This is the chemical addiction.
Takes around a hundred days for the brain to rewire itself. Every time you smoke, it's day one again. The habit part is the urge to light up when you get in a car, after a meal, etc. Your hand reaches instinctively for a pocket. The skin crawling, brain fog and irrational behavior are part of the chemical addiction.
You can break a habit by conscious behavior regulation in about seven days. Replacing a habit with another habit is one of the easiest ways to break a habit.
Nicotine gum exchanges habits without dealing with the chemical addiction. The key is to switch habits from grabbing a cigarette to grabbing a stick of gum instinctively and then replace the nicotine gum with regular gum. Every time you grab a stick of nicotine gum you are starting at zero in terms of the time it takes for the brain to rewire itself. The only way to stop using nicotine is to stop using nicotine. There is no cutting back, and weaning oneself off of it, once full chemical addiction takes place.
The first three days are the worst, the next 4 to six are moderately bad, and then for about 40 more days the cravings will get weaker and weaker and come less often. The nicotine dreams or random cravings and the odd impulse to stop at the store and buy a pack will persist for 90 to 100 days.
Alcohol is comparatively a cake walk. Do three to seven days dealing with the skin crawlies and insanity and you have that part of it licked. But a drink puts you back at square one, every time. An alcoholic can self regulate, but the chemical addiction is maintained. An alcoholic can drink "a couple" to defeat the skin crawlies, at 4 o'clock, or whenever the habitual time is, and string alcoholism along for infinity (or until liver failure). Life events and opportunity trigger heavier drinking. IE, a four day weekend allows starting at breakfast and staying drunk until passout time on the last day of the stretch. Family conflict or vehicle failure can make the normal loading dose, of a couple, to maintain/satisfy the chemical cravings, turn into a fifth, or a 24 pack. As time passes, the triggering factors for heavy drinking become less and less significant. The loading dose increases. Hiding alcohol consumption from others kicks in. Feelings of guilt and shame kick in. The thought process changes from "look at me, I'm the life of the party", to "I'm a stinky, no account drunk". This leads to depression, which gets self medicated with the cause of the depression. It is a more heavily mood altering addiction than nicotine addiction, and a little harder to decide to combat, but a little easier to combat once that decision is made.
The decision can only be made by the individual. Any attempt by outsiders is met with some crazy defensive behavior. I have no doubt that Tolkein had dealt with addiction, either personally or through someone he was close to, when he made the Smeagol character. The source of your addiction is "your precious", and any attempt to separate you from "your precious" is viewed as an attack, and draws you closer to "your precious". Even hospitalization or incarceration can fail to break the cycle of addiction, if the addict decides to go find "the precious" as soon as he is released. They have to decide on their own that their precious is killing them, and that they need to stay the H away from that substance at all costs, despite cravings, peer pressure, or calamity. That switch has to click for the cycle to be broken. Takes death in some instances.