A story that I heard years ago:
Once there was a really bad storm that left thousands of starfish stranded on a beach. They could survive there for a while, but they wouldn't make it until the tide came in, and several were past the point where the tide would ever reach them. After the storm had passed, a boy was on the beach. He picked up a starfish and threw it back into the sea, and then another, and another. He kept doing this over and over again. An older man showed up on the beach and saw what the boy was doing. He went up to the boy and laughed, saying "My boy, look at all of these starfish. You'll never be able to save them all. Do you really think you can make a difference?" The boy looked up at the man while throwing another starfish into the sea, and said, "I just made a difference for that one." He bent over to pick up another starfish, and threw it into the water, "I just made a difference for that one, too."
How often do we see things happening around us that seem insurmountable, and therefore we do nothing, because we think doing something small is the same as doing nothing at all?