GM CEO Mary Barra has led through decades of crises — and her leadership playbook is simple: do the right thing (even when it's hard), solve problems fast, stay transparent… and obsess over the customer. Because as Barra puts it: "The customer tells us when we win." What’s the No. 1 leadership lesson you've learned the hard way? 👇 Tune in to CNBC Leaders Playbook — a new primetime TV series hosted by Julia Boorstin where top business leaders break down how success is built. Only on CNBC. cnb.cx