From talking to a buddy at work, what you always wish for when it comes true may not be the greatest thing you could imagine anymore. From taking an economics course, I remember the concept of the law of diminishing returns. This is pretty much how when you are satisfied with a demand. From constantly being fed that demand, it gradually lessens.
There's also something called sticky demand from what I remember. These markets are pretty much dealing with those dangerous and highly addictive drugs. It's like you can't get enough of it and want always more. It's a highly profitable field to exploit like some criminals have in the past, but it's life threatening and not enough addicts are responsible about maintaining their own health, so it's illegal.
Yeah, about the mind, it's really to hard to control urges and go after doing the right thing. Once you get sucked into something that really brings you some sort of accomplishment and well-being, it's just hard to be challenged by someone to abandon that. Imagine someone like Christ popped up in your life and told you everything you were doing was wrong, it would be something you either ignore or feel really offended by. What about the other end, where you do actually care about what he said and wanted to listen and change your ways?