be a wake-up call

To trigger a sense of urgency or the motivation in someone to realize something or make a change. Harold's sudden chest pain was a real wake-up call—now, he exercises consistently and eats a healthier diet. This financial crisis will surely be a wake-up call to governments around the world to start regulating their markets more strictly. That terrible car accident was just the wake-up call I needed to quit my boring office job and start acting again.