It is what you read when you don’t have to that determines what you will be when you can’t help it.

Charles Francis Potter (1885-1962) American Unitarian minister, theologian, humanist, activist

Speech, Dayton, Ohio (Apr 1927)

Often misattributed to Oscar Wilde. More discussion here: What You Read When You Don’t Have To, Determines What You Will Be When You Can’t Help It – Quote Investigator