An unhappy childhood is a writer's gold mine. This nugget can be traced back to the July 1949 edition of the Partisan Review, a now defunct American periodical devoted to politics and literature. It comes from a book review entitled "Twenty-Seven Stories", in which Isaac Rosenfeld deliberates the merits of Nineteen Stories by Graham Greene and A Tree of Night and Other Stories by Truman Capote. The full sentence reads: "An unhappy childhood is a writer's gold mine, and one valuable thing Greene gets out of it is an honest basis for his stories." Like many an aphorism, it's a quote taken out of context.
As a writer, you create your own context, but in doing so you strip real events of their contexts, use people as models for your characters, even relocate buildings or reroute rivers, all in the service of your prose.