Speaking about or in the film Darfur Now, Don Cheadle hopes that people "will realize that they can do something more than nothing." This simple and obvious phrase has stuck with me.
In Lions for Lambs I saw this same theme of people wanting to contribute something or make a difference to improve the world. There is so much that needs to be done, but there is so much that can be done.
Whatever your passion is, whatever gets you upset or strikes you at the core--do something about it, for it, or to fight against it. And then try to do at least a little something once in a while for some of those things you're not so passionate about.