However, I'd recommend revisiting your entire thought process about this stuff the very first time you break one of your rules (like when you take them twice in a month for that one "really exceptional" situation).
It's called a slippery slope rather than a precipitous drop for a reason and people don't get addicted to drugs because they're "not smart".
x pills is fine, y pills is fine, z pills makes you a "complete moron".
However I think you're over simplifying the question. Not everyone has the same response to drugs/substances. Some people can do what systematical does without any long term side effects because they simply have the willpower, self awareness, and personality type that allows them to avoid becoming dependent.
Conversely other people would become dependent and turn into complete wrecks almost over night. Similar things can be said for alcohol, or any other "altered stated". It doesn't necessarily mean that the substance itself is the problem, or that all use is "abuse".
It really comes down to knowing yourself, knowing your own limits, and being as well informed as you can be.
i considered that this might be overly semantic. but if not definitively incorrect, it is at the very least profoundly tactless.