I'm not sure how addiction plays into that. Perhaps it's more a matter of "how strong is your desire to quit" and your own level of will power.
Desire and willpower have almost nothing to do with the ability to quit an addiction, typically. Addiction is an extremely complex thing, but one of things that research has pretty clearly shown is that people who fail to beat their addiction (to whatever), aren't failing because they lack the desire or willpower in most cases.
Some people have a fairly easy time overcoming addiction, and for some it's the next best thing to impossible. There are many reasons that mix together to cause this, some having to do with personality, some with biology, and some with environment.
I cringe when people say that addiction is "all in the mind," because in the first place, that's not precisely true, but also because it's overly trivializing the problem. The implication is that since it's purely mental, then it isn't a real problem. After all, it's all in your mind, so just change your mind!
