Some ideas: * Listen to them, have a conversation about optimal work life balance. * Think about your habits, ask if you're working too much, too little, or just the right amount. * Ask yourself every hour that you work if you think that hour had been productive, or if you have been unproductively "working" due to exhaustion. * Consider having all of these conversations after a vacation or some other form of time off, because it's easy to be myopic when you're in the middle of working.