Promotions should come with a health warning, experts say, with modern CEOs increasingly becoming frazzled, run down, and prone to accelerated aging and serious illnesses. "Probably two-thirds of CEOs are struggling," says one researcher. "... People assume CEOs are superhuman, but they're grappling with a really hard job." The best way to avoid a breakdown? Build a support network -- drawing on the likes of personal trainers and trusted confidantes -- and try to maintain a healthy work-life balance, experts say.