We can obsess over the details until hell freezes over. (that's meant as a joke, here at the Christian forum...)
I'll go back to my original response. There are matters of morality that can be defined right off, i.e: murder,adultery,and all that other good stuff. And then there's the stuff that doesn't really cause harm to anybody else but ourselves, this is probably harder to define as "sin". Does it kill me slowly by habitual usage, or will it kill me right away or in a relatively short period of time. In these cases I would suspect it's a matter of conscience, what does my inner voice say? Is this *wrong*? If I really think it is, then I must find a way to stop it. But know what, I'm not one who thinks of everything in terms of black and white.