I was watching a movie about a police officer. Every day he goes out onto the streets to keep the peace. He never knows what the day might bring. Each day might be his last. Every time he captures a criminal, a new one invariably takes the old one's place.
It's never ending, yet this officer is at peace. He's not trying to save the world. He's not even trying to change it. He knows that's impossible. He does his job, and will continue to do his job until he can't.
I think that is a brilliant way to approach life.