I can't remember what I can't forget

Something popped into my head tonight, and it won't leave. Well, the essence of something. I don't remember the exact words, but it was more or less "we cannot change the world, we can only live our lives." I wish I could remember. The point was that any cultural change has to start out small. Perhaps it was "...we can only change minds"? Where is my memory when I need it?