The points about the waste of time are points well made. At some point, wasted time amounts to a wasted life.
My experience with drugs is vicarious, but that does not mean that I have not observed how the effects vary in detail by coincide in general. The dissolution of ambition and discipline seem universal in my acquaintances who have histories of what I shall euphemistically call "more than occasional social consumption." The few prodigies of my acquaintance (damned few) do not seem to have been influenced as badly in this regard, and I attribute that to the simple fact that they did not have to work as hard as did those less gifted. The average and less-than-average guys I grew up with, many of which are some few years younger than I and went through a more "focused" trial in the seventies than did I (I spent much of the sixties in the military before VN had time to destroy discipline, and I returned to civilian life far more mature than my confrčres). Most seem to have struggled somewhat over the years since, and most still offer unconvincing defenses about their conduct and attitudes during that "missing" decade.
The "problem" then was far less daunting, and far less dangerous, than it seems now to be. The explosion of profit and competition to constantly raise the ante with newer and more fearsome addictives followed these "pioneers" of the illicit trades; back then, it seems to me, most of the available stuff was "softer" than now. Most of my friends did not dabble in heroin, cocaine or opium, but eagerly sought out marijuana and even hasheesh, which early on was harder to obtain than the former (which was everywhere). As the markets grew, however, the trade exploded exponentially. I would hate like hell to have kids to counsel now. Jack Weinberg famously said, "don't trust anyone over thirty" (a comment often wrongly attributed to either Jerry Rubin or Abby Hoffman), he was being facetious but expressing a reality that we all know to be true to the creed of nearly all adolescents.
Jeez, am I happy to be an OF that needs only to worry about the shit they're filling me with. That's enough of a task for me to handle.