Have you heard the story of the girl throwing starfish back in the ocean?
It's a parable about how some people will scoff at others trying to help because it won't solve the entire problem. And the moral of the story is that being a useful person isn't about being able to solve entire crises, but doing your bit of good in the ways that you are able and how that multiplies when many individuals do the same.
We focus so much sometimes on the hugeness of the issues in front of us that we forget we can (and should) do things because they are the right thing to do.
We can just do a little bit, and it adds up.