"The world" in this context is really "other humans". If you can't imagine any way you can make even one other life better in some way, then you really haven't thought about it enough. It is through these small acts of kindness that the world is transformed - as rob05c said above - it's how we made civilisation in the first place.
Everyone's gonna die. But if you do something to make someone's life better, there's a good chance that they will do the same, before they die. That ripple can extend to infinity, to a kind of immortality, and it's the only way we can build the Star Trek future that we all want. You don't have to do it - but you can. [edit] I am reminded by this of a wonderful quote from Harry S. Truman : "It is amazing what you can accomplish if you do not care who gets the credit."