In his childhood he envied the smokers and became addicted. Here is a fine biographical gem — the source of his tobacco money:
"The Rebbe, R. Zalman of blessed memory, would hand over to his scribes in writing the sermon he had preached on the Sabbath… and afterward they would sell the manuscripts to the visiting Hasidim… I was one of the copyists, and I earned enough to buy tobacco…" AZR, "On Three Things," "Collected Writings" (5695); Project Ben-Yehuda. (The Rebbe = R. Shneur Zalman of Lyady.)
He became a "bound slave" to tobacco, suffered on Sabbaths, and was afflicted with headaches and coughing, until one day "I threw away the tobacco… and behold, I was freed from slavery, healed of my pains, and with the pennies I saved I could buy a book."
Here is the biographical origin of his vegetarianism — a surgical operation some 20 years earlier:
"Twenty years ago I underwent an operation… the physician Dr. Wallach advised me not to eat meat for three months… and I became convinced that in truth there is no need at all to eat meat… the killing of animals… was always repugnant to me." Ibid. (Complements the origin story in "Vegetarianism.")
The moral foundation — extending "Thou shalt not kill" to animals — is grounded in a quotation from the "Tzemach Tzedek" ("Pri HaAretz") and in the story of the child who was sent to slaughter a hen:
"He looked, and his whole body trembled; he took the hen, carried it some distance, cast it away and fled." Ibid. — the healthy, innocent instinct against slaughter.
AZR abstained from drinking alcohol entirely, out of respect for the intellect given to him:
"I do not wish to ruin the good gift that the Holy One, blessed be He, gave me — a little intellect and understanding — by means of drink… I can rejoice and dance in a time of gladness even without that contemptible trick of drunkenness." Ibid.