When the time comes, AND if it's brought up,tell them you "Learned the error of your ways, and don't do that anymore." The test will show it's been 2 months since you "sinned", and will show that you have no "addiction". Tell them it was a "stupid kid thing, and you didn't like it anyways, you regret it, blahblahblah. They eat that shit up, and I'm sure they'll see it as a "youthful indiscretion". Avoid it til then, and you'll be ok. Good luck, and God Bless you and yours.
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Let me get this straight, I can go to the store and buy a bottle of legal poison and get drunk, and buy a pack of cancer, but I can't use a plant that grows wild in the ditch and has never killed anyone? Hypocrisy is never intelligent.