I think you'll find that there are no physiological withdrawal symptoms with cocaine addiction, unlike pretty much any other drug or alcohol addiction, and so hence, to some degree, a large part of it is the willpower to not continue doing it.
Your brain wants it, but it's not as though you actually feel ill, or are unable to function without it.
Simply not true. Prolonged cocaine use affects the receptors in the brain. There is a physical change. This is why it is considered the most addictive drug.