It's an old argument... but one that is more myth than reality.
Almost nobody can control how cautious and responsible they are with drugs.
1) you don't control the supply, so you never know if you'll end up with a tainted supply
2) you don't control your own body's reactions to the drugs, so you never know when you will have tipped the balance from "in control" to "addicted" - and addiction can happen on many levels, not just physical addiction.
3) as with anything that alters our mental state, we become less aware of it's impact on us. Yes, legal medications can be just as big an issue - but those are "supposed to be" under the direct supervision of a physician who is "supposed" to know what to watch for. (yes, not all physicians manage the medications right either - and yes there can be serious problems as a result)
At 17, you feel invincible. Like most 17 year olds (yes, I'm the parent of teenagers...) you think us "old folks" don't know what we're talking about, especially about things like drugs. You don't realize that many of us came of age in the "golden age" of drug use... we've been around it all our lives, just as you have... but we've lived a few more years and seen a few more things happen.
Why would drug use (legal or illegal, and considering alcohol and tobacco as legal drugs) be so important to you, when it has so many potentially devastating consequences?
That's essentially the stand I've taken with my own teenagers.
