To be honest, except for her calypso music in the 1950's, I've always found Angelou a minor writer for whom I can summon no quotations from memory.
Bonus: This insane gibberish from a defensive bureaucrat -
A spokesman for the Postal Service, Mark Saunders, did not deny that the quotation may have originated with Anglund. "Had we known about this issue beforehand, we would have used one of [Angelou’s] many other works," he said. "The sentence held great meaning for her and she is publicly identified with its popularity."