“Wrong and inappropriate use has caused LSD to become my problem child.”
Foreword
LSD : My Problem Child (1980)
Context: Deliberate provocation of mystical experience, particularly by LSD and related hallucinogens, in contrast to spontaneous visionary experiences, entails dangers that must not be underestimated. Practitioners must take into account the peculiar effects of these substances, namely their ability to influence our consciousness, the innermost essence of our being. The history of LSD to date amply demonstrates the catastrophic consequences that can ensue when its profound effect is misjudged and the substance is mistaken for a pleasure drug. Special internal and external advance preparations are required; with them, an LSD experiment can become a meaningful experience. Wrong and inappropriate use has caused LSD to become my problem child.
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Albert Hofmann 42
Swiss chemist 1906–2008Related quotes

LSD psychotherapy (1980), MAPS 2001 edition, Epilogue, p. 299.

Attributed to Leary by Terence McKenna in one of his talks ( "The World and Its Double" https://terencemckenna.wikispaces.com/The+World+And+Its+Double, 11 September 1993, Nature Friends Lodge, Sierra Madre, CA), though he also stated[citation needed] Leary denied ever having said it.
Misattributed
Think Better: An Innovator's Guide to Productive Thinking

“… mothers are often fondest of the child which has caused them the greatest pain.”
Source: The Hunchback of Notre-Dame

“Hate, it has caused a lot of problems in the world, but has not solved one yet.”
Nearly identical quote attributed to a 1995 TV show, Touched by an Angel https://www.imdb.com/title/tt0732136/quotes: Tess: No, hate has caused a lot of problems in this world, but it's never solved one yet.
Misattributed