Talk show host Larry King says the heart attack he suffered last month has taught him a lesson in survival: He quit smoking, changed his diet and began regular exercise. "I'd have to be an idiot to ignore what this is telling me. This is a great lesson, a painful lesson, if you can live through it. I'm lucky," King said in his weekly USA Today column on Monday. King, 53, says he once thought life had granted him a built-in immunity.