How hard it is depends on whether you're a real alcoholic. Most people who drink a lot aren't. Alcohol is actually easier to quit than cigarettes if you just drink it because you choose to (like people who drink because they are unhappy, or bored/frustrated), or have a craving.

But real alcoholism is worse than even heroin addiction. It is probably the drug that is the hardest to quit on your own once you have a real addiction. Some people also seem to be immune to alcoholism, and never form a real dependency. My grandparents used to drink daily for decades; my grandmother became an alcoholic, while my grandfather, who drank more, easily quit once problems with her alcoholism started. He missed drinking but he had no withdrawal symptoms. On the other hand, she had to be hospitalized for the first month or so because she was in danger of dying or murdering someone (she had tried to murder my grandfather with a knife simply because he wouldn't let her have a drink). It had very little to do with willpower, and more to do with how their nervous systems were differently affected by decades of drinking.