“If we can believe in the Gnostic gospel of Thomas, old Uncle Jesus said, "If you bring forth what is inside you, what you bring forth will save you. If you don't bring forth what is inside you, what you bring forth can destroy you.”
Source: Bird by Bird: Some Instructions on Writing and Life
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Anne Lamott 146
Novelist, essayist, memoirist, activist 1954Related quotes
Source: Queen of Dreams

Earliest attribution found in Who Said That?: More than 2,500 Usable Quotes and Illustrations https://books.google.nl/books?id=7mn8AwAAQBAJ&pg=PT63 (1995) by George Sweeting. Online sources always attribute the quote to Augustine, but never specify in which of his works it is to be found.
Disputed

Happier Than The Morning Sun
Song lyrics, Music of My Mind (1972)