But most people can't change the world. Most individuals shouldn't have the power to change the world. What we can do is be a force for good in the lives that are proximal to us. If we can make a few people's lives better, we should rest easy knowing that we've done our part.
If we can do more than that, then great. But never let the overwhelming hugeness of the entire world cripple your ability to make your little dent. Most people only get the chance to make a little dent - if that - and there's nothing wrong with that.