Do not take harmful drugs

People who take drugs do not always see the real world in front of them. They are not really there. On a highway, in casual contact, in a home, they can be very dangerous to you. People mistakenly believe they “feel better” or “act better” or are “only happy” when on drugs. This is just another delusion. Sooner or later the drugs will destroy them physically. Discourage people from taking drugs. When they are doing so, encourage them to seek help in getting off them.

— L. Ron Hubbard
From The Way to Happiness,
A nonreligious, common-sense moral code