Brazilian writer Paulo Coelho’s books — in particular, his beloved 1988 bestseller, “The Alchemist” — are infused with a spirituality that has resonated with millions of readers. In 2017 he took to Twitter to offer his followers this piece of advice. “Smile is the way to solve many problems,” he wrote. “Silence is the way to avoid many problems.” Coelho reminds us that the power of words can cut both ways, and the discretion to know when to keep quiet and offer a kind smile is just as valuable.