“If I had been smarter then I would have let research fail regularly. That would have been more realistic, more rational and more cunning. But I could not do that. I had become a junkie.”

Silence and Awakening
The Inevitable: Contemporary Writer Confront Death (2011) Edited by David Shields & Bradford Morrow

Source: The Uplift War (1987), Chapter 110 (p. 626)

According to The Quote Verifier (2006) by Ralph Keyes, Einstein never said any such thing. (According to p. 285 of the book's "source notes" Keyes checked New Statesman 16 April 1965, which is commonly cited as the source of this quote. Some other books claim it is from New Statesman 16 April 1955 and at least one has it as 1945, but a Google Books search http://books.google.com/advanced_book_search?num=10&q=einstein+watchmaker+%22new+statesman%22 with the date range restricted to 1900-1995 shows that all the earliest sources give it as 1965. This includes the earliest source located, The Penguin Dictionary of Modern Quotations from 1971, as can be verified by this search http://www.google.com/search?q=%22of+his+making+the+atom+bomb+possible.+quoted+in+new+statesman%2C+16+april+1965%22&btnG=Search+Books&tbm=bks&tbo=1.) Keyes notes that Einstein "did use similar words to make a very different point" when he wrote, in a 1954 letter to the editor at The Reporter magazine, "If I would be a young man again and had to decide how to make my living, I would not try to become a scientist or scholar or teacher. I would rather choose to be a plumber or a peddler in the hope to find that modest degree of independence still available under present circumstances."
Similarly, in Einstein and the Poet by William Hermanns, p. 86 http://books.google.com/books?id=QXCyjj6T5ZUC&lpg=PP1&pg=PA86#v=onepage&q&f=false, Einstein is quoted saying the following in a 1948 interview: "If I should be born again, I will become a cobbler and do my thinking in peace."
Misattributed
Variant: If only I had known, I should have become a watchmaker.

Source: Howards End (1910), Ch. 11
Context: He remembered his wife's even goodness during thirty years. Not anything in detail — not courtship or early raptures —but just the unvarying virtue, that seemed to him a woman's noblest quality. So many women are capricious, breaking into odd flaws of passion or frivolity. Not so his wife. Year after year, summer and winter, as bride and mother, she had been the same, he had always trusted her. Her tenderness! Her innocence! The wonderful innocence that was hers by the gift of God. Ruth knew no more of worldly wickedness and wisdom than did the flowers in her garden, or the grass in her field. Her idea of business — "Henry, why do people who have enough money try to get more money?" Her idea of politics — "I am sure that if the mothers of various nations could meet, there would be no more wars," Her idea of religion — ah, this had been a cloud, but a cloud that passed. She came of Quaker stock, and he and his family, formerly Dissenters, were now members of the Church of England. The rector's sermons had at first repelled her, and she had expressed a desire for "a more inward light," adding, "not so much for myself as for baby" (Charles). Inward light must have been granted, for he heard no complaints in later years. They brought up their three children without dispute. They had never disputed.
She lay under the earth now. She had gone, and as if to make her going the more bitter, had gone with a touch of mystery that was all unlike her.

Source: Last Sacrifice

Black Boy (1945)

Source: Participant observer, 1994, p. 242; As cited in: Ickis (2014)

14m15s https://www.youtube.com/watch?v=eazIth4orfM#t=14m15s
Power to the Pixel (2009)

A BBC quote in Flying Sikh': Indian sprinter Milkha Singh biopic set for release."